A landscape assessment of CTSA evaluators and their work in the CTSA consortium, 2021 survey findings.

This article presents a landscape assessment of the findings from the 2021 Clinical and Translational Science Award (CTSA) Evaluators Survey. This survey was the most recent iteration of a well established, national, peer-led systematic snapshot of the CTSA evaluators, their skillsets, listed evaluation resources, preferred methods, and identified best practices. Three questions guided our study: who are the CTSA evaluators, what competencies do they share and how is their work used within hubs. We describe our survey process (logistics of development, deployment, and differences in historical context with prior instruments); and present its main findings. We provide specific recommendations for evaluation practice in two main categories (National vs Group-level) including, among others, the need for a national, strategic plan for evaluation as well as enhanced mentoring and training of the next generation of evaluators. Although based on the challenges and opportunities currently within the CTSA Consortium, takeaways from this study constitute important lessons with potential for application in other large evaluation consortia. To our knowledge, this is the first time 2021 survey findings are disseminated widely, to increase transparency of the CTSA evaluators' work and to motivate conversations within hub and beyond, as to how best to leverage existent evaluative capacity.

Learning health system benefits: Development and initial validation of a framework.

Introduction: Implementation of research findings in clinical practice often is not realized or only partially achieved, and if so, with a significant delay. Learning health systems (LHSs) hold promise to overcome this problem by embedding clinical research and evidence-based best practices into care delivery, enabling innovation and continuous improvement. Implementing an LHS is a complex process that requires participation and resources of a wide range of stakeholders, including healthcare leaders, clinical providers, patients and families, payers, and researchers. Engaging these stakeholders requires communicating clear, tangible value propositions. Existing models identify broad categories of benefits but do not explicate the full range of benefits or ways they can manifest in different organizations. Methods: To develop such a framework, a working group with representatives from six Clinical and Translational Science Award (CTSA) hubs reviewed existing literature on LHS characteristics, models, and goals; solicited expert input; and applied the framework to their local LHS experiences. Results: The Framework of LHS Benefits includes six categories of benefits (quality, safety, equity, patient satisfaction, reputation, and value) relevant for a range of stakeholders and defines key concepts within each benefit. Applying the framework to five LHS case examples indicated preliminary face validity across varied LHS approaches and revealed three dimensions in which the framework is relevant: defining goals of individual LHS projects, facilitating collaboration based on shared values, and establishing guiding tenets of an LHS program or mission. Conclusion: The framework can be used to communicate the value of an LHS to different stakeholders across varied contexts and purposes, and to identify future organizational priorities. Further validation will contribute to the framework's evolution and support its potential to inform the development of tools to evaluate LHS impact.

Mitochondrial ncRNA LDL-805 declines in alveolar epithelial type 2 cells of chronic obstructive pulmonary disease patients.

Rationale: We showed that levels of a murine mitochondrial noncoding RNA, mito-ncR-LDL805 , increase in alveolar epithelial type 2 cells exposed to extracts from cigarette smoke. The transcripts translocate to the nucleus, upregulating nucleus-encoded mitochondrial genes and mitochondrial bioenergetics. This response is lost after chronic exposure to smoke in a mouse model of chronic obstructive pulmonary disease. Objectives: To determine if mito-ncR-LDL805 plays a role in human disease, this study aimed to (i) identify the human homologue, (ii) test if the smoke-induced response occurs in human cells, (ii) determine causality between the subcellular localization of the transcript and increased mitochondrial bioenergetics, and (iii) analyze mito-ncR-LDL805 transcript levels in samples from patients with chronic obstructive pulmonary disease. Methods: Levels and subcellular localization of the human homologue identified from an RNA transcript library were assessed in human alveolar epithelial type 2 cells exposed to smoke extract. Lipid nanoparticles were used for nucleus-targeted delivery of mito-ncR-LDL805 transcripts. Analyses included in situ hybridization, quantitative PCR, cell growth, and Seahorse mitochondrial bioenergetics assays. Measurements and Main Results: The levels of human homologue transiently increased and the transcripts translocated to the nuclei in human cells exposed to smoke extract. Targeted nuclear delivery of transcripts increased mitochondrial bioenergetics. Alveolar cells from humans with chronic obstructive pulmonary disease had reduced levels of the mito-ncR-LDL805 . Conclusions: mito-ncR-LDL805 mediates mitochondrial bioenergetics in murine and human alveolar epithelial type 2 cells in response to cigarette smoke exposure, but this response is likely lost in diseases associated with chronic smoking, such as chronic obstructive pulmonary disease, due to its diminished levels. Impact: This study describes a novel mechanism by which epithelial cells in the lungs adapt to the mitochondrial stress triggered by exposure to cigarette smoke. We show that a noncoding RNA in mitochondria is upregulated and translocated to the nuclei of alveolar epithelial type 2 cells to trigger expression of genes that restore mitochondrial bioenergetics. Mitochondria function and levels of the noncoding RNA decrease under conditions that lead to chronic obstructive pulmonary disease, suggesting that the mitochondrial noncoding RNA can serve as potential therapeutic target to restore function to halt disease progression.

Implementing the learning health system paradigm within academic health centers.

Introduction: The learning health system (LHS) concept represents a bold innovation that combines organizational learning, strategic analysis of patient data, stakeholder engagement and the systematic translation of research into practice - all in service of improving the quality of health care delivered across the organization. This innovation has been diffused and widely adopted by healthcare organizations over the past 15 years, but academic health centers (AHCs) have been slower on the uptake. The irony is that AHCs have the resources (e.g., trained researchers, sophisticated clinical data systems, informatics infrastructure) that are necessary to do the highest-quality and most impactful LHS work. Methods: Based on a review of publications describing how AHCs have implemented LHS work, as well as the authors' direct experience promoting the adoption of the LHS paradigm at Atrium Health Wake Forest Baptist (AHWFB), we:identify a set of factors that have inhibited broader adoption of the LHS paradigm among AHCs; distinguish between the forms of LHS work that are consistent and inconsistent with the mission of AHCs; and offer recommendations for broader adoption and fuller implementation of the LHS paradigm. Results: The LHS paradigm represents an expansion of the scientific paradigm which serves as the foundation of research enterprise within AHCs. Both paradigms value rigorous studies of new treatments and practices, including pragmatic clinical trials. The LHS paradigm also places a high value on quality improvement studies, organizational learning, and the translation of research findings into improved patient care and operations within the local health system. The two paradigms differ on the origin of the research question, i.e., a pressing patient-care issue facing the health system versus the investigator's own research interests. Academic researchers have been disincentivized from pursuing at least some forms of LHS research. However, a growing number of AHCs are finding ways to integrate the LHS paradigm into their research enterprise, either by providing research faculty with institutional funding to cover their effort on studies that address the health system's priority issues, or by establishing an institute dedicated to LHS research. Conclusions: The LHS paradigm is a disruptive intervention for AHCs, one that was initially resisted but is increasingly being embraced. AHCs are developing strategies for conducting LHS research, typically in parallel to the more traditional biomedical science that is core to academic medicine. Full implementation of the LHS paradigm will require further alignment between LHS and science, including a shift in the criteria for promotion and tenure to support those researchers who choose to focus on the pressing issues facing the health system.

Protein disulfide isomerase family mediated redox regulation in cancer.

Protein disulfide isomerase (PDI) and its superfamilies are mainly endoplasmic reticulum (ER) resident proteins with essential roles in maintaining cellular homeostasis, via thiol oxidation/reduction cycles, chaperoning, and isomerization of client proteins. Since PDIs play an important role in ER homeostasis, their upregulation supports cell survival and they are found in a variety of cancer types. Despite the fact that the importance of PDI to tumorigenesis remains to be understood, it is emerging as a new therapeutic target in cancer. During the past decade, several PDI inhibitors has been developed and commercialized, but none has been approved for clinical use. In this review, we discuss the properties and redox regulation of PDIs within the ER and provide an overview of the last 5 years of advances regarding PDI inhibitors.

Effectiveness of extended postpartum inpatient monitoring for hypertensive disorders of pregnancy to reduce the risk of readmission for preeclampsia with severe features.

BACKGROUND: Preeclampsia is an obstetrical disorder, which complicates 3% to 6% of pregnancies and contributes to 21.6% of readmissions in the postpartum period. The optimal strategy for inpatient monitoring of blood pressures to minimize readmissions for postpartum patients with hypertensive disorders is not known. We hypothesized that extended monitoring of postpartum patients with hypertensive disorders of pregnancy for at least 36 hours after the last blood pressure that was ≥150/100 mm Hg would result in decreased readmission rates for preeclampsia with severe features compared with those who were not observed by these blood pressure goals. OBJECTIVE: This study aimed to evaluate whether extended inpatient monitoring of postpartum patients with hypertensive disorders of pregnancy for at least 36 hours after their last blood pressure that was ≥150/100 mm Hg would improve readmission rates for preeclampsia with severe features within 6 weeks of delivery. STUDY DESIGN: This was a retrospective cohort study in patients with a singleton pregnancy and a diagnosis of a hypertensive disorder of pregnancy at their delivery admission or at any point during pregnancy who delivered 1 year before and 1 year after the implementation of extended inpatient monitoring of postpartum hypertension. The primary outcome was readmission for preeclampsia with severe features within 6 weeks of delivery. The secondary outcomes were length of stay during first admission, number of readmissions for any indication, intensive care unit admission, postpartum day at readmission, median systolic blood pressure in the 24-hour period before discharge, median diastolic blood pressure in the 24-hour period before discharge, intravenous antihypertensive medication required during first admission, and intravenous antihypertensive medication required during second admission. Univariable analysis was performed for the association between baseline maternal characteristics and the primary outcome. Multivariable analysis was performed, adjusting for baseline maternal characteristic differences between exposure groups. RESULTS: A total of 567 patients met the inclusion criteria of which 248 patients delivered before and 319 delivered after the implementation of extended monitoring. For baseline characteristics, the extended monitoring group had a significantly higher proportion of patients who were non-Hispanic Black and Hispanic, more diagnoses of hypertensive disorders and/or diabetes mellitus at the time of admission for delivery, a difference in the distribution of hypertensive diagnoses at the time of discharge from the first admission, and fewer discharged patients from their first admission on labetalol than the preintervention group. In a univariable analysis of the primary outcome, there was a significantly increased risk of readmission for preeclampsia with severe features in the extended monitoring group (62.5% vs 96.2% of total readmissions; P=.004). In multivariable analysis, patients in the extended monitoring group were more likely to be readmitted for preeclampsia with severe features than patients in the preintervention group (adjusted odds ratio, 3.45; 95% confidence interval, 1.03-11.5; P=.044). CONCLUSION: Extended monitoring with a strict blood pressure goal of <150/<100 mm Hg did not decrease readmissions for preeclampsia with severe features in patients with a previous diagnosis of a hypertensive disorder of pregnancy.

Consulting parents bereaved by childhood cancer: A qualitative study to improve bereavement services.

Twelve Australian parents bereaved by childhood cancer were interviewed about their experiences of, and preferences for, bereavement support, to inform recommendations to improve bereavement care. Reflexive thematic analysis resulted in five themes: Care, empathy, and connection assist with bereavement; Communication makes a difference; Early and ongoing support is desired; Gender matters when grieving the loss of a child; and The pull of peer support. Parents can be assisted through empathy, early and ongoing support, enhanced communication, peer support, and care that is inclusive of all genders. Parents in non-metropolitan areas require increased and flexible support options.

Clarifying the concept of a learning health system for healthcare delivery organizations: Implications from a qualitative analysis of the scientific literature.

The "learning health system" (LHS) concept has been defined in broad terms, which makes it challenging for health system leaders to determine exactly what is required to transform their organization into an LHS. This study provides a conceptual map of the LHS landscape by identifying the activities, principles, tools, and conditions that LHS researchers have associated with the concept. Through a multi-step screening process, two researchers identified 79 publications from PubMed (published before January 2020) that contained information relevant to the question, "What work is required of a healthcare organization that is operating as an LHS?" Those publications were coded as to whether or not they referenced each of 94 LHS elements in the taxonomy developed by the study team. This taxonomy, named the Learning Health Systems Consolidated Framework (LHS-CF), organizes the elements into five "bodies of work" (organizational learning, translation of evidence into practice, building knowledge, analyzing clinical data, and engaging stakeholders) and four "enabling conditions" (workforce skilled for LHS work, data systems and informatics technology in place, organization invests resources in LHS work, and supportive organizational culture). We report the frequency that each of the 94 elements was referenced across the 79 publications. The four most referenced elements were: "organization builds knowledge or evidence," "quality improvement practices are standard practice," "patients and family members are actively engaged," and "organizational culture emphasizes and supports learning." By dissecting the LHS construct into its component elements, the LHS-CF taxonomy can serve as a useful tool for LHS researchers and practitioners in defining the aspects of LHS they are addressing. By assessing how often each element is referenced in the literature, the study provides guidance to health system leaders as to how their organization needs to evolve in order to become an LHS - while also recognizing that each organization should emphasize elements that are most aligned with their mission and goals.

A Synthetic Small RNA Homologous to the D-Loop Transcript of mtDNA Enhances Mitochondrial Bioenergetics.

Mitochondrial malfunction is a hallmark of many diseases, including neurodegenerative disorders, cardiovascular and lung diseases, and cancers. We previously found that alveolar progenitor cells, which are more resistant to cigarette smoke-induced injury than the other cells of the lung parenchyma, upregulate the mtDNA-encoded small non-coding RNA mito-ncR-805 after exposure to smoke. The mito-ncR-805 acts as a retrograde signal between the mitochondria and the nucleus. Here, we identified a region of mito-ncR-805 that is conserved in the mammalian mitochondrial genomes and generated shorter versions of mouse and human transcripts (mmu-CR805 and hsa-LDL1, respectively), which differ in a few nucleotides and which we refer to as the "functional bit". Overexpression of mouse and human functional bits in either the mouse or the human lung epithelial cells led to an increase in the activity of the Krebs cycle and oxidative phosphorylation, stabilized the mitochondrial potential, conferred faster cell division, and lowered the levels of proapoptotic pseudokinase, TRIB3. Both oligos, mmu-CR805 and hsa-LDL1 conferred cross-species beneficial effects. Our data indicate a high degree of evolutionary conservation of retrograde signaling via a functional bit of the D-loop transcript, mito-ncR-805, in the mammals. This emphasizes the importance of the pathway and suggests a potential to develop this functional bit into a therapeutic agent that enhances mitochondrial bioenergetics.

Altered redox regulation and S-glutathionylation of BiP contribute to bortezomib resistance in multiple myeloma.

Multiple myeloma (MM) cells have high rates of secretion of proteins rich in disulfide bonds and depend upon compartmentalized redox balance for accurate protein folding. The proteasome inhibitor bortezomib (Btz) is a successful frontline treatment for the disease, but its long-term efficacy is restricted by the acquisition of resistance. We found that MM cell lines resistant to Btz maintain high levels of oxidative stress and are cross resistant to endoplasmic reticulum (ER) stress-inducing agents thapsigargin (ThG), and tunicamycin (TuM). Moreover, cells expressing high/wild type levels of glutathione S-transferase P (GSTP) are more resistant than Gstp1/p2 knockout cells. In agreement, basal levels of S-glutathionylated proteins and redox regulation enzymes, including GSTP are elevated at mRNA and protein levels in resistant cells. GSTP mediated S-glutathionylation (SSG) regulates the activities of a number of redox active ER proteins. Here we demonstrated that the post-translational modification determines the balance between foldase and ATPase activities of the binding immunoglobulin protein (BiP), with Cys41-SSG important for ATPase, and Cys420-SSG for foldase. BiP expression and S-glutathionylation are increased in clinical specimens of bone marrow from MM patients compared to non-cancerous samples. Preventing S-glutathionylation in MM cells with a GSTP specific inhibitor restored BiP activities and reversed resistance to Btz. Therefore, S-glutathionylation of BiP confers pro-survival advantages and represents a novel mechanism of drug resistance in MM cells. We conclude that altered GSTP expression leads to S-glutathionylation of BiP, and contributes to acquired resistance to Btz in MM.

Hidden Markov Models Reveal Tactical Adjustment of Temporally Clustered Courtship Displays in Response to the Behaviors of a Robotic Female.

We present a statistical approach-a custom-built hidden Markov model (HMM)-that is broadly applicable to the analysis of temporally clustered display events, as found in many animals, including birds, orthopterans, and anurans. This HMM can simultaneously estimate both the expected lengths of each animal's display bouts and their within-bout display rates. We highlight the HMM's ability to estimate changes in animals' display effort over time and across different social contexts, using data from male greater sage grouse (Centrocercus urophasianus). Male display effort was modeled across three sites in two experimental treatments (robotic female simulating interested or uninterested behavior) and in the presence or absence of live females. Across contexts, we show that sage grouse males primarily adjust their bout lengths rather than their within-bout display rates. Males' responses to female behavior were correlated with male mating success: males with more matings showed high display persistence regardless of female behavior, while males with fewer matings tended to invest selectively in females that were already showing interest in mating. Additionally, males with higher mating success responded more to the presence of a female than males with fewer matings did. We conclude with suggestions for adapting our HMM approach for use in other animal systems.

Home Safety Fall and Accident Risk Among Prematurely Aging, Formerly Homeless Adults.

OBJECTIVE: Homelessness prematurely ages people. A large subgroup of formerly homeless adults between ages 40 and 64 yr have health conditions similar to or worse than people categorized as elderly. Little is known about the impact of this group's chronic health conditions on their ability to safely function in supportive housing. METHOD: Home safety visits were carried out with 25 formerly homeless adults, ages 40-64 yr, now residing in supportive housing. RESULTS: Participants had physical, cognitive, and mental health problems that significantly interfered with their ability to perform daily life skills, safely function in an apartment, and manage chronic health conditions. Home safety hazards included cluttered walking paths, the presence of steps, and the lack of grab bars and nonskid flooring. CONCLUSION: The homeless population would benefit from aging specialists, such as occupational therapists, who could help people to maintain and function more safely in their homes. Without such services, this population may be at risk for home safety events leading to hospitalization and mortality.

GADD34 Function in Protein Trafficking Promotes Adaptation to Hyperosmotic Stress in Human Corneal Cells.

GADD34, a stress-induced regulatory subunit of the phosphatase PP1, is known to function in hyperosmotic stress through its well-known role in the integrated stress response (ISR) pathway. Adaptation to hyperosmotic stress is important for the health of corneal epithelial cells exposed to changes in extracellular osmolarity, with maladaptation leading to dry eye syndrome. This adaptation includes induction of SNAT2, an endoplasmic reticulum (ER)-Golgi-processed protein, which helps to reverse the stress-induced loss of cell volume and promote homeostasis through amino acid uptake. Here, we show that GADD34 promotes the processing of proteins synthesized on the ER during hyperosmotic stress independent of its action in the ISR. We show that GADD34/PP1 phosphatase activity reverses hyperosmotic-stress-induced Golgi fragmentation and is important for cis- to trans-Golgi trafficking of SNAT2, thereby promoting SNAT2 plasma membrane localization and function. These results suggest that GADD34 is a protective molecule for ocular diseases such as dry eye syndrome.

Adverse Outcomes Associated with Cigarette Smoke Radicals Related to Damage to Protein-disulfide Isomerase.

Identification of factors contributing to the development of chronic obstructive pulmonary disease (COPD) is crucial for developing new treatments. An increase in the levels of protein-disulfide isomerase (PDI), a multifaceted endoplasmic reticulum resident chaperone, has been demonstrated in human smokers, presumably as a protective adaptation to cigarette smoke (CS) exposure. We found a similar increase in the levels of PDI in the murine model of COPD. We also found abnormally high levels (4-6 times) of oxidized and sulfenilated forms of PDI in the lungs of murine smokers compared with non-smokers. PDI oxidation progressively increases with age. We begin to delineate the possible role of an increased ratio of oxidized PDI in the age-related onset of COPD by investigating the impact of exposure to CS radicals, such as acrolein (AC), hydroxyquinones (HQ), peroxynitrites (PN), and hydrogen peroxide, on their ability to induce unfolded protein response (UPR) and their effects on the structure and function of PDIs. Exposure to AC, HQ, PN, and CS resulted in cysteine and tyrosine nitrosylation leading to an altered three-dimensional structure of the PDI due to a decrease in helical content and formation of a more random coil structure, resulting in protein unfolding, inhibition of PDI reductase and isomerase activity in vitro and in vivo, and subsequent induction of endoplasmic reticulum stress response. Addition of glutathione prevented the induction of UPR, and AC and HQ induced structural changes in PDI. Exposure to PN and glutathione resulted in conjugation of PDI possibly at active site tyrosine residues. The findings presented here propose a new role of PDI in the pathogenesis of COPD and its age-dependent onset.

Cigarette smoke exposure during pregnancy alters fetomaternal cell trafficking leading to retention of microchimeric cells in the maternal lung.

Cigarette smoke exposure causes chronic oxidative lung damage. During pregnancy, fetal microchimeric cells traffic to the mother. Their numbers are increased at the site of acute injury. We hypothesized that milder chronic diffuse smoke injury would attract fetal cells to maternal lungs. We used a green-fluorescent-protein (GFP) mouse model to study the effects of cigarette smoke exposure on fetomaternal cell trafficking. Wild-type female mice were exposed to cigarette smoke for about 4 weeks and bred with homozygote GFP males. Cigarette smoke exposure continued until lungs were harvested and analyzed. Exposure to cigarette smoke led to macrophage accumulation in the maternal lung and significantly lower fetal weights. Cigarette smoke exposure influenced fetomaternal cell trafficking. It was associated with retention of GFP-positive fetal cells in the maternal lung and a significant reduction of fetal cells in maternal livers at gestational day 18, when fetomaternal cell trafficking peaks in the mouse model. Cells quickly clear postpartum, leaving only a few, difficult to detect, persisting microchimeric cells behind. In our study, we confirmed the postpartum clearance of cells in the maternal lungs, with no significant difference in both groups. We conclude that in the mouse model, cigarette smoke exposure during pregnancy leads to a retention of fetal microchimeric cells in the maternal lung, the site of injury. Further studies will be needed to elucidate the effect of cigarette smoke exposure on the phenotypic characteristics and function of these fetal microchimeric cells, and confirm its course in cigarette smoke exposure in humans.

Cigarette smoking affects oxidative protein folding in endoplasmic reticulum by modifying protein disulfide isomerase.

The endoplasmic reticulum (ER) stress response (ERSR) and associated protein aggregation, is under investigation for its role in human diseases, including chronic obstructive pulmonary disease (COPD) where cigarette smoking (CS) is a risk factor for disease development. Our hypothesis states that CS-associated oxidative stress interferes with oxidative protein folding in the ER and elicits ERSR. We investigated ERSR induction following acute CS exposure and delineated mechanisms of CS-induced ERSR. Lung lysates from mice exposed or not to one cigarette were tested for activation of the ERSR. Up to 4-fold increase in phosphorylation of eIF2α and nuclear form of ATF6 was detected in CS-exposed animals. CS affected the formation of disulfide bonds through excessive posttranslational oxidation of protein disulfide isomerase (PDI). Increased amounts of complexes between PDI and its client proteins persisted in CS-exposed samples. BiP was not a constituent of these complexes, demonstrating the specificity of the early effects of CS exposure on ER. Disturbances in protein folding were accompanied by changes in the organization of ER network and ER exit sites. Our results provide evidence that ERSR is induced early in response to CS exposure and identifies the first known ER-resident target of CS PDI, demonstrating that CS affects oxidative protein folding.

Cigarette smoke inhibits engulfment of apoptotic cells by macrophages through inhibition of actin rearrangement.

Exposure to cigarette smoke (CS) was shown to impair the capacity of macrophages to clear bacteria and apoptotic cells. Here, we show that both the exposure of macrophages to cigarette smoke extract (CSE) in vitro and an acute single exposure to CS in vivo impair the macrophage clearance of apoptotic polymorphonuclear leukocytes (PMNs). Upon longer periods of exposure to smoke in vivo (4-12 weeks), the impaired capacity of macrophages to clear apoptotic cells persisted after the cessation of smoking, with slow recovery to normality observed 4 weeks later. With respect to the mechanism by which CS impairs the macrophage uptake of apoptotic PMNs, we did not detect altered surface expression of receptors associated with apoptotic cell clearance. We did observe the impaired phosphorylation of the guanine nucleotide exchange factor Vav1 and the downstream inhibition of Ras-related C3 botulinum toxin substrate 1 (Rac1) activation. Consistent with these findings, CS impaired the macrophage cytoskeletal changes observed after stimulation with apoptotic cells. A loss of actin occurred at the leading edge, manifested as impaired ruffling of the cell membrane and a decreased capacity to engulf apoptotic cells. The inability to clear PMNs would lead to a greater release of destructive PMN products, and would diminish the reparative phenotype induced by the macrophage clearance of apoptotic cells.

Phosphatidylinositol 4-phosphate formation at ER exit sites regulates ER export.

The mechanisms that regulate endoplasmic reticulum (ER) exit-site (ERES) assembly and COPII-mediated ER export are currently unknown. We analyzed the role of phosphatidylinositols (PtdIns) in regulating ER export. Utilizing pleckstrin homology domains and a PtdIns phosphatase to specifically sequester or reduce phosphorylated PtdIns levels, we found that PtdIns 4-phosphate (PtsIns4P) is required to promote COPII-mediated ER export. Biochemical and morphological in vitro analysis revealed dynamic and localized PtsIns4P formation at ERES. PtdIns4P was utilized to support Sar1-induced proliferation and constriction of ERES membranes. PtdIns4P also assisted in Sar1-induced COPII nucleation at ERES. Therefore, localized dynamic remodeling of PtdIns marks ERES membranes to regulate COPII-mediated ER export.

Distinct Golgi populations of phosphatidylinositol 4-phosphate regulated by phosphatidylinositol 4-kinases.

Phosphatidylinositol 4-phosphate (PI4P) regulates biosynthetic membrane traffic at multiple steps and differentially affects the surface delivery of apically and basolaterally destined proteins in polarized cells. Two phosphatidylinositol 4-kinases (PI4Ks) have been localized to the Golgi complex in mammalian cells, type III PI4Kbeta (PI4KIIIbeta) and type II PI4Kalpha (PI4KIIalpha). Here we report that PI4KIIIbeta and PI4KIIalpha localize to discrete subcompartments of the Golgi complex in Madin-Darby canine kidney (MDCK) cells. PI4KIIIbeta was enriched in early Golgi compartments, whereas PI4KIIalpha colocalized with markers of the trans-Golgi network (TGN). To understand the temporal and spatial control of PI4P generation across the Golgi complex, we quantitated the steady state distribution of a fluorescent PI4P-binding domain relative to cis/medial Golgi and TGN markers in transiently transfected MDCK cells. The density of the signal from this PI4P reporter was roughly 2-fold greater in the early Golgi compartments compared with that of the TGN. Furthermore, this ratio could be modulated in vivo by overexpression of catalytically inactive PI4KIIIbeta and PI4KIIalpha or in vitro by the PI4KIIIbeta inhibitor wortmannin. Our data suggest that both PI4KIIIbeta and PI4KIIalpha contribute to the compartmental regulation of PI4P synthesis within the Golgi complex. We discuss our results with respect to the kinetic effects of modulating PI4K activity on polarized biosynthetic traffic in MDCK cells.