Cell-selective proteomics segregates pancreatic cancer subtypes by extracellular proteins in tumors and circulation.

Cell-selective proteomics is a powerful emerging concept to study heterocellular processes in tissues. However, its high potential to identify non-cell-autonomous disease mechanisms and biomarkers has been hindered by low proteome coverage. Here, we address this limitation and devise a comprehensive azidonorleucine labeling, click chemistry enrichment, and mass spectrometry-based proteomics and secretomics strategy to dissect aberrant signals in pancreatic ductal adenocarcinoma (PDAC). Our in-depth co-culture and in vivo analyses cover more than 10,000 cancer cell-derived proteins and reveal systematic differences between molecular PDAC subtypes. Secreted proteins, such as chemokines and EMT-promoting matrisome proteins, associated with distinct macrophage polarization and tumor stromal composition, differentiate classical and mesenchymal PDAC. Intriguingly, more than 1,600 cancer cell-derived proteins including cytokines and pre-metastatic niche formation-associated factors in mouse serum reflect tumor activity in circulation. Our findings highlight how cell-selective proteomics can accelerate the discovery of diagnostic markers and therapeutic targets in cancer.

Influence of circadian clocks on adaptive immunity and vaccination responses.

The adaptive immune response is under circadian control, yet, why adaptive immune reactions continue to exhibit circadian changes over long periods of time is unknown. Using a combination of experimental and mathematical modeling approaches, we show here that dendritic cells migrate from the skin to the draining lymph node in a time-of-day-dependent manner, which provides an enhanced likelihood for functional interactions with T cells. Rhythmic expression of TNF in the draining lymph node enhances BMAL1-controlled ICAM-1 expression in high endothelial venules, resulting in lymphocyte infiltration and lymph node expansion. Lymph node cellularity continues to be different for weeks after the initial time-of-day-dependent challenge, which governs the immune response to vaccinations directed against Hepatitis A virus as well as SARS-CoV-2. In this work, we present a mechanistic understanding of the time-of-day dependent development and maintenance of an adaptive immune response, providing a strategy for using time-of-day to optimize vaccination regimes.

P38 kinases mediate NLRP1 inflammasome activation after ribotoxic stress response and virus infection.

Inflammasomes integrate cytosolic evidence of infection or damage to mount inflammatory responses. The inflammasome sensor NLRP1 is expressed in human keratinocytes and coordinates inflammation in the skin. We found that diverse stress signals induce human NLRP1 inflammasome assembly by activating MAP kinase p38: While the ribotoxic stress response to UV and microbial molecules exclusively activates p38 through MAP3K ZAKα, infection with arthropod-borne alphaviruses, including Semliki Forest and Chikungunya virus, activates p38 through ZAKα and potentially other MAP3K. We demonstrate that p38 directly phosphorylates NLRP1 and that serine 107 in the linker region is critical for activation. NLRP1 phosphorylation is followed by ubiquitination of NLRP1PYD, N-terminal degradation of NLRP1, and nucleation of inflammasomes by NLRP1UPA-CARD. In contrast, activation of NLRP1 by nanobody-mediated ubiquitination, viral proteases, or inhibition of DPP9 was independent of p38 activity. Taken together, we define p38 activation as a unifying signaling hub that controls NLRP1 inflammasome activation by integrating a variety of cellular stress signals relevant to the skin.

High Na+ Environments Impair Phagocyte Oxidase-Dependent Antibacterial Activity of Neutrophils.

Infection and inflammation can augment local Na+ abundance. These increases in local Na+ levels boost proinflammatory and antimicrobial macrophage activity and can favor polarization of T cells towards a proinflammatory Th17 phenotype. Although neutrophils play an important role in fighting intruding invaders, the impact of increased Na+ on the antimicrobial activity of neutrophils remains elusive. Here we show that, in neutrophils, increases in Na+ (high salt, HS) impair the ability of human and murine neutrophils to eliminate Escherichia coli and Staphylococcus aureus. High salt caused reduced spontaneous movement, degranulation and impaired production of reactive oxygen species (ROS) while leaving neutrophil viability unchanged. High salt enhanced the activity of the p38 mitogen-activated protein kinase (p38/MAPK) and increased the interleukin (IL)-8 release in a p38/MAPK-dependent manner. Whereas inhibition of p38/MAPK did not result in improved neutrophil defense, pharmacological blockade of the phagocyte oxidase (PHOX) or its genetic ablation mimicked the impaired antimicrobial activity detected under high salt conditions. Stimulation of neutrophils with phorbol-12-myristate-13-acetate (PMA) overcame high salt-induced impairment in ROS production and restored antimicrobial activity of neutrophils. Hence, we conclude that high salt-impaired PHOX activity results in diminished antimicrobial activity. Our findings suggest that increases in local Na+ represent an ionic checkpoint that prevents excessive ROS production of neutrophils, which decreases their antimicrobial potential and could potentially curtail ROS-mediated tissue damage.

Identification of covalent modifications regulating immune signaling complex composition and phenotype.

Cells signal through rearrangements of protein communities governed by covalent modifications and reversible interactions of distinct sets of proteins. A method that identifies those post-transcriptional modifications regulating signaling complex composition and functional phenotypes in one experimental setup would facilitate an efficient identification of novel molecular signaling checkpoints. Here, we devised modifications, interactions and phenotypes by affinity purification mass spectrometry (MIP-APMS), comprising the streamlined cloning and transduction of tagged proteins into functionalized reporter cells as well as affinity chromatography, followed by MS-based quantification. We report the time-resolved interplay of more than 50 previously undescribed modification and hundreds of protein-protein interactions of 19 immune protein complexes in monocytes. Validation of interdependencies between covalent, reversible, and functional protein complex regulations by knockout or site-specific mutation revealed ISGylation and phosphorylation of TRAF2 as well as ARHGEF18 interaction in Toll-like receptor 2 signaling. Moreover, we identify distinct mechanisms of action for small molecule inhibitors of p38 (MAPK14). Our method provides a fast and cost-effective pipeline for the molecular interrogation of protein communities in diverse biological systems and primary cells.

Proteomics reveals distinct mechanisms regulating the release of cytokines and alarmins during pyroptosis.

A major pathway for proinflammatory protein release by macrophages is inflammasome-mediated pyroptotic cell death. As conventional secretion, unconventional secretion, and cell death are executed simultaneously, however, the cellular mechanisms regulating this complex paracrine program remain incompletely understood. Here, we devise a quantitative proteomics strategy to define the cellular exit route for each protein by pharmacological and genetic dissection of cellular checkpoints regulating protein release. We report the release of hundreds of proteins during pyroptosis, predominantly due to cell lysis. They comprise constitutively expressed and transcriptionally induced proteins derived from the cytoplasm and specific intracellular organelles. Many low-molecular-weight proteins including the cytokine interleukin-1ß, alarmins, and lysosomal-cargo proteins exit cells in the absence of cell lysis. Cytokines and alarmins are released in an endoplasmic reticulum (ER)-Golgi-dependent manner as free proteins rather than by extracellular vesicles. Our work provides an experimental framework for the dissection of cellular exit pathways and a resource for pyroptotic protein release.

Cholesterol sensing by CD81 is important for hepatitis C virus entry.

CD81 plays a central role in a variety of physiological and pathological processes. Recent structural analysis of CD81 indicates that it contains an intramembrane cholesterol-binding pocket and that interaction with cholesterol may regulate a conformational switch in the large extracellular domain of CD81. Therefore, CD81 possesses a potential cholesterol-sensing mechanism; however, its relevance for protein function is thus far unknown. In this study we investigate CD81 cholesterol sensing in the context of its activity as a receptor for hepatitis C virus (HCV). Structure-led mutagenesis of the cholesterol-binding pocket reduced CD81-cholesterol association but had disparate effects on HCV entry, both reducing and enhancing CD81 receptor activity. We reasoned that this could be explained by alterations in the consequences of cholesterol binding. To investigate this further we performed molecular dynamic simulations of CD81 with and without cholesterol; this identified a potential allosteric mechanism by which cholesterol binding regulates the conformation of CD81. To test this, we designed further mutations to force CD81 into either the open (cholesterol-unbound) or closed (cholesterol-bound) conformation. The open mutant of CD81 exhibited reduced HCV receptor activity, whereas the closed mutant enhanced activity. These data are consistent with cholesterol sensing switching CD81 between a receptor active and inactive state. CD81 interactome analysis also suggests that conformational switching may modulate the assembly of CD81-partner protein networks. This work furthers our understanding of the molecular mechanism of CD81 cholesterol sensing, how this relates to HCV entry, and CD81's function as a molecular scaffold; these insights are relevant to CD81's varied roles in both health and disease.

NCX1 represents an ionic Na+ sensing mechanism in macrophages.

Inflammation and infection can trigger local tissue Na+ accumulation. This Na+-rich environment boosts proinflammatory activation of monocyte/macrophage-like cells (MΦs) and their antimicrobial activity. Enhanced Na+-driven MΦ function requires the osmoprotective transcription factor nuclear factor of activated T cells 5 (NFAT5), which augments nitric oxide (NO) production and contributes to increased autophagy. However, the mechanism of Na+ sensing in MΦs remained unclear. High extracellular Na+ levels (high salt [HS]) trigger a substantial Na+ influx and Ca2+ loss. Here, we show that the Na+/Ca2+ exchanger 1 (NCX1, also known as solute carrier family 8 member A1 [SLC8A1]) plays a critical role in HS-triggered Na+ influx, concomitant Ca2+ efflux, and subsequent augmented NFAT5 accumulation. Moreover, interfering with NCX1 activity impairs HS-boosted inflammatory signaling, infection-triggered autolysosome formation, and subsequent antibacterial activity. Taken together, this demonstrates that NCX1 is able to sense Na+ and is required for amplifying inflammatory and antimicrobial MΦ responses upon HS exposure. Manipulating NCX1 offers a new strategy to regulate MΦ function.

Female sex, young age, northern German residence, hypoglycemia and disabling diabetes complications are associated with depressed mood in the WHO-5 questionnaire - A multicenter DPV study among 17,563 adult patients with type 2 diabetes.

BACKGROUND: Like other mental illnesses, depression is a culturally sensitive topic. Hence, findings cannot be transferred between countries. We investigated the frequency of depressed mood and its association with diabetes-related factors in a large type 2 diabetes (T2D) cohort from real-life care in Germany. METHODS: 17,563 adults (median [IQR]: 64.5[55.9-71.1] years) from the multicenter diabetes follow-up registry, DPV (diabetes prospective follow-up), were investigated. All had completed the WHO-5 questionnaire, a screening tool for depression. Logistic regression was applied to study the association of demographic and diabetes-related factors with depressed mood (SAS 9.4). P<0.05 was considered significant. RESULTS: Using a WHO-5 cut-off of <13, 27.4% of patients were at risk for depressed mood. A clinical depression diagnosis was recognized in 8.4%. Female sex (OR: 1.5[95%-CI: 1.4-1.6]), young age (1.2[1.1-1.4]), longer diabetes duration (1.2[1.1-1.3]), and living in Northern Germany (1.3[1.2-1.4]) were each associated with increased odds for depressed mood. After adjusting for these confounders, worse glycemic control (1.4[1.3-1.5]), insulin use (1.3[1.2-1.4]), myocardial infarction (1.3[1.2-1.5]), stroke (1.8[1.5-2.0]), retinopathy (1.4[1.3-1.6]), renal failure (1.4[1.2-1.8]), diabetic foot syndrome (1.3[1.2-1.4]), severe hypoglycemia (1.5[1.2-1.9]), two or more inpatient admissions (2.1[1.8-2.4]), and longer duration of hospital stay (1-<14 days: 1.3[1.2-2.3]; >14 days: 2.1[1.9-2.3]) were related to depressed mood. LIMITATION: Due to the cross-sectional design, no causality can be drawn. CONCLUSIONS: In T2D, depressed mood is not uncommon. However, in routine care a clinical depression might be missed and regular screening is advisable. Besides the well-known associations with depressed mood, northern German residence and mainly life-compromising diabetes comorbidities were identified as related factors.

Psoriasis and Diabetes: A Multicenter Study in 222078 Type 2 Diabetes Patients Reveals High Levels of Depression.

OBJECTIVE: This study aimed to investigate the association between psoriasis and disease outcome in type 2 diabetes (T2D). METHODS: 222078 T2D patients (≥10 years old) from the prospective, multicenter diabetes patient registry were analyzed. Specific search items were used to identify psoriasis patients. Multiple regression models were fitted and adjusted for demographic confounder. RESULTS: 232 T2D patients had comorbid psoriasis. After adjusting psoriasis patients revealed a higher BMI (31.8 [31.0; 32.6] versus 30.6 [30.5; 30.6] kg/m2, p = 0.004) and HbA1c (64.8 [62.1; 67.6] versus 59.0 [58.9; 59.1] mmol/mol, p < 0.0001). Insulin was used more frequently (62.3 [55.7; 68.5] versus 50.9 [50.7; 51.1] %, p = 0.001), only OAD/GLP-1 was similar, and nonpharmacological treatment was less common (13.3 [9.5; 18.3] versus 21.9 [21.7; 22.1] %, p = 0.002). Severe hypoglycemia (0.31 [0.238; 0.399] versus 0.06 [0.057; 0.060] events per patient-year, p < 0.0001), hypertension (86.1 [81.1; 90.0] versus 68.0 [67.8; 68.2] %, p < 0.0001), and thyroid disease (14.0 [10.1; 19.2] versus 4.6 [4.5; 4.7] %, p < 0.0001) were more prevalent. Depression occurred more often (10.5 [7.1; 15.2] versus 2.8 [2.7; 2.8] %, p < 0.0001). CONCLUSIONS: Clinical diabetes characteristics in psoriasis T2D patients were clearly worse compared to patients without psoriasis. Comorbid conditions and depression were more prevalent, and more intensive diabetes therapy was required.

Heart rate, ejection duration and subendocardial viability ratio in patients with rheumatoid arthritis as compared to controls.

AIM: Rheumatoid arthritis (RA) is associated with increased cardiovascular morbidity and mortality. In the general population, an increased heart rate is associated with increased mortality. Only a few studies have investigated heart rate in RA patients and compared the results with patients that do not have RA (n-RA). Therefore, little is known as to whether an increased heart rate, at least in part, could explain the increased mortality found in RA patients. The aim of the present study was to investigate whether heart rate is increased in RA patients. METHODS: In this cross-sectional study, heart rate was determined in a total of 282 patients (131 RA, 151 n-RA). In addition, non-invasive pulse wave analysis of the radial artery was performed to determine cardiac ejection duration using the Sphygmocor apparatus. Furthermore, the subendocardial viability ratio (SEVR), a marker of cardiac workload, was investigated, whereby higher values indicate a more favorable supply/demand relationship for the myocardium. Patients using chronotropic drugs were not included in the study. RESULTS: Heart rate was virtually the same in RA patients (71.9 ± 11.2 beats/min [bpm]) as compared with controls (72.3 ± 11.7 bpm; P > 0.05). Also SEVR (RA 144 ± 25% vs. n-RA 147 ± 27%; P > 0.05) and ejection duration (RA 321 ± 24 ms vs. n-RA 318 ± 24 ms; P > 0.05) were comparable between the groups. CONCLUSION: It could not be shown that heart rate in RA patients differs significantly from heart rate in controls. Therefore, heart rate does not appear to explain or contribute to the increased cardiovascular risk found in RA patients.

Rheumatoid arthritis is an independent risk factor for an increased augmentation index regardless of the coexistence of traditional cardiovascular risk factors.

BACKGROUND: Rheumatoid arthritis (RA) is associated with increased cardiovascular morbidity. It was previously shown that the augmentation index (AIx), a marker of vascular dysfunction, is higher in RA patients without traditional cardiovascular risk factors than in healthy controls. In this study we determined whether the impact of RA on the AIx is diminished in the context of coexisting, strong cardiovascular risk factors. PATIENTS AND METHODS: A total of 411 participants were included [203 with RA; 208 in the non-RA (n-RA) group]. Pulse-wave analysis was performed on the radial artery using applanation tonometry. The impact of RA on the AIx was determined in a single and in a multiple linear regression model. RESULTS: The mean unadjusted AIx was 30.5 ± 9.0% for RA patients and 24.0 ± 11.0% for the n-RA group (P < 0.001). In the regression model, the following variables are statistically significant at approximately the same level (P < 0.001); the order of impact of these variables is age > diastolic blood pressure > sex > RA > height > smoking status. RA, height, and smoking had a nearly equal impact on the AIx. CONCLUSIONS: The AIx is increased in RA patients regardless of the coexistence of traditional cardiovascular risk factors, thereby reflecting vascular dysfunction in this population. The impact of RA on the vascular system is comparable to that of smoking.