Mycotic Aortic Aneurysm Secondary to Salmonella enterica Infection: A Case Report and Treatment Approach.

Mycotic (infected) aortic aneurysm is a severe clinical condition with high morbidity and mortality. Salmonella spp. is a Gram-negative, rod-shaped bacteria that is typically limited to the gastrointestinal tract and resolves spontaneously but can progress to invasive infections such as bacteremia. Serious complications may arise, particularly in debilitated, elderly, and neonatal patients. We describe the case of a 74-year-old female with a history of diabetes and hypertension who presented with shortness of breath, fever, chills, abdominal pain, vomiting, and diarrhea. The patient's blood culture tested positive for Salmonella enterica, and she was given ceftriaxone based on the results, but he remained symptomatic. A computed tomography scan of the chest with contrast revealed a mycotic aneurysm of the thoracic aorta. The patient was urgently transferred to a higher level of care and underwent emergency thoracic endovascular aortic repair with stenting and intravenous antibiotics. The presence of an infected aneurysm and associated abscess formation in such high-risk patients makes the endovascular approach more suitable than other options such as open surgery, aneurysmal excision and ligation without arterial reconstruction, excision with immediate reconstruction, and excision with interval reconstruction.

Ulinastatin ameliorated streptozotocin-induced diabetic nephropathy: Potential effects via modulating the components of gut-kidney axis and restoring mitochondrial homeostasis.

Growing evidence supports the role of the gut-kidney axis and persistent mitochondrial dysfunction in the pathogenesis of diabetic nephropathy (DN). Ulinastatin (UTI) has a potent anti-inflammatory effect, protecting the kidney and the gut barrier in sepsis, but its effect on DN has yet to be investigated. This study aimed to assess the potential mitigating effect of UTI on DN and investigate the possible involvement of gut-kidney axis and mitochondrial homeostasis in this effect. Forty male Wistar rats were divided equally into four groups: normal; UTI-treated control; untreated DN; and UTI-treated DN. At the end of the experiment, UTI ameliorated DN by modulating the gut-kidney axis as it improved serum and urinary creatinine, urine volume, creatinine clearance, blood urea nitrogen, urinary albumin, intestinal morphology including villus height, crypt depth, and number of goblet cells, with upregulating the expression of intestinal tight-junction protein claudin-1, and counteracting kidney changes as indicated by significantly decreasing glomerular tuft area and periglomerular and peritubular collagen deposition. In addition, it significantly reduced intestinal and renal nuclear factor kappa B (NF-κB), serum Complement 5a (C5a), renal monocyte chemoattractant protein-1 (MCP-1), renal intercellular adhesion molecule 1 (ICAM1), and renal signal transducer and activator of transcription 3 (STAT3), mitochondrial dynamin related protein 1 (Drp1), mitochondrial fission 1 protein (FIS1), mitochondrial reactive oxygen species (ROS), renal hydrogen peroxide (H2O2), and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels. Furthermore, it significantly increased serum short chain fatty acids (SCFAs), and mitochondrial ATP levels and mitochondrial transmembrane potential. Moreover, there were significant correlations between measured markers of gut components of the gut-kidney axis and renal function tests in UTI-treated DN group. In conclusion, UTI has a promising therapeutic effect on DN by modulating the gut-kidney axis and improving renal mitochondrial dynamics and redox equilibrium.

The cardioprotective effect of human glucagon-like peptide-1 receptor agonist (semaglutide) on cisplatin-induced cardiotoxicity in rats: Targeting mitochondrial functions, dynamics, biogenesis, and redox status pathways.

The cardiotoxic effect of chemotherapeutic agents as cisplatin has become a major issue recently. Interference with mitochondrial dynamics, biogenesis, redox status, and apoptosis are the most possible underlying mechanisms. Semaglutide is a human glucagon-like peptide-1 receptor agonist (GLP-1R), which is used primarily for the treatment of DM. Various recent studies have investigated (GLP-1R) role in cardiovascular diseases due to antiapoptotic and antioxidant effects. The current study aimed to investigate the curative role of semaglutide's against cisplatin- induced cardiotoxicity and its relation to mitochondrial functions, dynamics, biogenesis, apoptosis, and redox status pathways. The study included 30 male rats divided into three groups: control, cisplatin-induced cardiotoxicity, and cisplatin-induced cardiotoxicity treated with semaglutide. At the end of the experiment heart index, serum cardiotoxicity markers, SOD, GPX activities and H2 O2 level were estimated. Mitochondrial transmembrane potential, complex I and citrate synthase enzyme activities, ATP level, Mfn2 in addition to PGC-1 α levels were assessed as biogenesis markers. Mitophagy markers PINK1 and Parkin mRNA gene expression were estimated. Histopathological examination of cardiac muscles of all studied groups and immunoassay of P53 and caspase 3 in cardiac tissue were examined to assess apoptosis. Cisplatin has disturbed mitochondrial function and dynamics, dysregulate redox status and induced mitophagy and apoptosis, in the other hand semaglutide treatment has normalized dysregulated mitochondrial function and dynamics, redox status and suppressed mitophagy and apoptosis. Semaglutide has ameliorative effect against cisplatin- induced cardiotoxicity via modulation of mitochondrial functions, dynamics, biogenesis, apoptosis, and redox status pathways.

The prospective effect of fucoidan on splenic dysfunction caused by oxaliplatin in male rats through endoplasmic stress dynamics.

Fucoidans (FUCs) are highly sulfated polysaccharides demonstrating multiple actions in different systems. Oxaliplatin (OXA) is a platinum-containing chemotherapeutic agent with several side effects that restrict its usage. The current study aimed to determine the potential effect of FUC in male rats with splenic dysfunction induced by OXA. Eighty adult male rats aged (8-9 weeks) weighing (190-230 g) were divided into four groups: (Group I: the control group): Rats were administrated normal saline; (Group II: controls treated by FUC): Rats were treated with FUC; (Group III: Splenic dysfunction group): Rats were treated with 8 mg/kg OXA. (IV: Splenic dysfunction treated by FUC): Rats were treated by OXA as Group III, then fucoidan was given. At the end of the experiment, blood was collected to determine red blood cells and white blood cells. Splenic tissues were divided into one part for biochemical assays, oxidative stress markers as MDA and catalase, inflammatory markers (TNF-alpha, IL6), and apoptotic markers (caspase 3) and gene expression of Nrf2, Mapk1 gene expression, and endoplasmic stress parameters and the other part was used for immunohistochemical and histopathological analysis. Compared to the OXA-induced splenic dysfunction group, FUC significantly decreased high levels of MDA, TNF- alpha, IL6, caspase-3, Mapk1, endoplasmic stress induced by OXA, and increased the level of catalase and Nrf2. Fucoidan has corrected the histopathological and immunohistochemical changes compared to the OXA-induced splenic dysfunction group. In conclusion, our findings suggest that fucoidan has a significant role in the treatment of splenic dysfunction induced by OXA.

Linking mitochondrial dynamics and fertility: promoting fertility by phoenixin through modulation of ovarian expression of GnRH receptor and mitochondrial dynamics proteins DRP-1 and Mfn-2.

Obesity is linked to reproductive disorders. Novel neuropeptide phoenixin demonstrated many therapeutic actions. In this study, we aim to evaluate phoenixin's potential effect in obesity-induced infertility through modulating mitochondrial dynamics. Ninety adult female rats were divided to 4 groups: (I), fed with normal pellet diet; (II), given phoenixin; (III), fed with high-fat diet. Rats that developed obesity and infertility were divided to 2 groups: (III-A), received no further treatment; (III-B), given phoenixin. Our results showed that phoenixin treatment in obese infertile rats significantly decreased serum levels of insulin and testosterone and ovarian levels of dynamin-related protein1(Drp1),reactive oxygen species ROS, TNF-α, MDA, and caspase-3. Phoenixin treatment also significantly increased serum estrogen progesterone, LH, and FSH together with ovarian levels of GnRH receptor (GnRHR), mitofusin2(Mfn2), mitochondrial transmembrane potential (ΔΨm), and electron transport chain (ETC) complex-I significantly when compared with obese group. Ovarian histopathological changes were similarly improved by phoenixin. Our data demonstrate phoenixin's role in improving obesity-induced infertility.

The Ameliorative Effect of Empagliflozin in Vigabatrin-Induced Cerebellar/Neurobehavioral Deficits: Targeting mTOR/AMPK/SIRT-1 Signaling Pathways.

Introduction. Vigabatrin (VGB) is an antiepileptic drug that acts to irreversibly inhibit the γ-aminobutyric acid (GABA) transaminase enzyme, elevating GABA levels. Broad studies have established that long-term treatment and/or high doses of VGB lead to variable visual defects. However, little attention has been paid to its other side effects, especially those demonstrating cerebellar involvement. Sodium glucose-linked co-transporter 2 (SGLT2) inhibitors are antidiabetic agents with protective effects far greater than expected based on their anti-hyperglycemic effect. Method. Our study herein was designed to investigate the possible ameliorative effect of empagliflozin, the SGLT2 inhibitors, in VGB-induced cerebellar toxicity. A total of 40 male Wistar rats were allocated equally into 4 groups: Group I: control group; Group II: VGB group; Group III empagliflozin treated VGB group; and Group IV: empagliflozin treated group. All groups were subjected to the detection of cerebellar messenger RNA gene expression of silent mating type information regulation 2 homolog 1 (SIRT1) and Nucleoporin p62 (P62). Mammalian target of rapamycin (mTOR), adenosine monophosphate-activated protein kinase (AMPK), and beclin1 levels were assessed by the ELISA technique while malondialdehyde (MDA) level and superoxide dismutase (SOD) activity were detected spectrophotometrically. Immuno-histochemical studies, focusing on glial fibrillary acidic protein (GFAP) and S100 were performed, and the optical color density and the mean area percentage of GFAP positive astrocytes and the number of S 100 positive cells were also counted. Results. Following empagliflozin treatment, we documented significant upregulation of both SIRT1 and P62 mRNA gene expression. Additionally, AMPK, Beclin1 levels, and SOD activity were significantly improved, while both mTOR and MDA levels were significantly reduced. Conclusions. We concluded for the first time that empagliflozin efficiently ameliorated the VGB-induced disrupted mTOR/AMPK/SIRT-1 signaling axis with subsequent improvement of the autophagy machinery and mitigation of the oxidative and inflammatory cellular environment, paving the way for an innovative therapeutic potential in managing VGB-induced neurotoxicity.

Cdc48/VCP and Endocytosis Regulate TDP-43 and FUS Toxicity and Turnover.

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron degenerative disease. TDP-43 (TAR DNA-binding protein 43) and FUS (fused in sarcoma) are aggregation-prone RNA-binding proteins that in ALS can mislocalize to the cytoplasm of affected motor neuron cells, often forming cytoplasmic aggregates in the process. Such mislocalization and aggregation are implicated in ALS pathology, though the mechanism(s) of TDP-43 and FUS cytoplasmic toxicity remains unclear. Recently, we determined that the endocytic function aids the turnover (i.e., protein degradation) of TDP-43 and reduces TDP-43 toxicity. Here, we identified that Cdc48 and Ubx3, a Cdc48 cofactor implicated in endocytic function, regulates the turnover and toxicity of TDP-43 and FUS expressed in Saccharomyces cerevisiae Cdc48 physically interacts and colocalizes with TDP-43, as does VCP, in ALS patient tissue. In yeast, FUS toxicity also depends strongly on endocytic function but not on autophagy under normal conditions. FUS expression also impairs endocytic function, as previously observed with TDP-43. Taken together, our data identify a role for Cdc48/VCP and endocytic function in regulating TDP-43 and FUS toxicity and turnover. Furthermore, endocytic dysfunction may be a common defect affecting the cytoplasmic clearance of ALS aggregation-prone proteins and may represent a novel therapeutic target of promise.

Correction to: Structural and functional aspects of the interaction partners of the small heat-shock protein in Synechocystis.

Table 1 in the original publication has been corrected.

Diagnostic Value of Glypican-3 for Hepatocellular Carcinomas

Background: Hepatocellular carcinoma (HCC) is a common and dangerous malignancy in many parts of the world, and especially in Egypt. Early diagnosis is the most important step in successful HCC management. However most cases are detected at late stage making effective intervention impossible. Aim: The aim of this study was to evaluate the potential of Glypican-3 (GPC-3) to aid in diagnosis of HCC, especially in patients with low serum alpha-fetoprotein (AFP). Subjects and methods: Serum GPC-3 was assessed by flow-cytometry and serum AFP by enzyme-linked immunosorbent assay (ELISA) in 40 HCC patients with AFP< 400ug\l. (GI), 40 HCC patients with AFP> 400ug\l. (GII) and 20 healthy controls (GIII). Results: GPC-3 was found to be significantly elevated in HCC as compared to healthy subjects (GI 38.2±22. 5, GII 50.2±22.6, and GIII 2.24±1.19), with sensitivities of 85% for GI and 84% for GII and specificities of 95% for GI and 92% for GII. AFP showed respective sensitivities of 50% and 79%, and specificities of 80% and 90%, for HCC diagnosis. The combination of GPC-3 with AFP achieved the highest sensitivity (98.5%) and specificity (97.8%). Conclusion: Serum GPC-3 has a better sensitivity than AFP for the diagnosis of HCC. Combination of two markers appears warranted for greatest accuracy.

Structural and functional aspects of the interaction partners of the small heat-shock protein in Synechocystis.

The canonical function of small heat-shock proteins (sHSPs) is to interact with proteins destabilized under conditions of cellular stress. While the breadth of interactions made by many sHSPs is well-known, there is currently little knowledge about what structural features of the interactors form the basis for their recognition. Here, we have identified 83 in vivo interactors of the sole sHSP in the cyanobacterium Synechocystis sp. PCC 6803, HSP16.6, reflective of stable associations with soluble proteins made under heat-shock conditions. By performing bioinformatic analyses on these interactors, we identify primary and secondary structural elements that are enriched relative to expectations from the cyanobacterial genome. In addition, by examining the Synechocystis interactors and comparing them with those identified to bind sHSPs in other prokaryotes, we show that sHSPs associate with specific proteins and biological processes. Our data are therefore consistent with a picture of sHSPs being broadly specific molecular chaperones that act to protect multiple cellular pathways.

Structural principles that enable oligomeric small heat-shock protein paralogs to evolve distinct functions.

Oligomeric proteins assemble with exceptional selectivity, even in the presence of closely related proteins, to perform their cellular roles. We show that most proteins related by gene duplication of an oligomeric ancestor have evolved to avoid hetero-oligomerization and that this correlates with their acquisition of distinct functions. We report how coassembly is avoided by two oligomeric small heat-shock protein paralogs. A hierarchy of assembly, involving intermediates that are populated only fleetingly at equilibrium, ensures selective oligomerization. Conformational flexibility at noninterfacial regions in the monomers prevents coassembly, allowing interfaces to remain largely conserved. Homomeric oligomers must overcome the entropic benefit of coassembly and, accordingly, homomeric paralogs comprise fewer subunits than homomers that have no paralogs.

Assessing Plant Tolerance to Acute Heat Stress.

It is well-established that plants are able to acclimate to temperatures above or below the optimal temperature for their growth. Here, we provide protocols for assays that can be used quantitatively or qualitatively to assess the relative ability of plants to acquire tolerance to high temperature stress. The hypocotyl elongation assay described was developed to screen for mutants defective in the acquisition of tolerance to extreme temperature stress, and other assays were developed to further characterize mutant and transgenic plants for heat tolerance of other processes or at other growth stages. Although the protocols provide details for application to Arabidopsis thaliana, the same basic methods can be adopted to assay heat tolerance in other plant species.

Class I and II Small Heat Shock Proteins Together with HSP101 Protect Protein Translation Factors during Heat Stress.

The ubiquitous small heat shock proteins (sHSPs) are well documented to act in vitro as molecular chaperones to prevent the irreversible aggregation of heat-sensitive proteins. However, the in vivo activities of sHSPs remain unclear. To investigate the two most abundant classes of plant cytosolic sHSPs (class I [CI] and class II [CII]), RNA interference (RNAi) and overexpression lines were created in Arabidopsis (Arabidopsis thaliana) and shown to have reduced and enhanced tolerance, respectively, to extreme heat stress. Affinity purification of CI and CII sHSPs from heat-stressed seedlings recovered eukaryotic translation elongation factor (eEF) 1B (α-, ß-, and γ-subunits) and eukaryotic translation initiation factor 4A (three isoforms), although the association with CI sHSPs was stronger and additional proteins involved in translation were recovered with CI sHSPs. eEF1B subunits became partially insoluble during heat stress and, in the CI and CII RNAi lines, showed reduced recovery to the soluble cell fraction after heat stress, which was also dependent on HSP101. Furthermore, after heat stress, CI sHSPs showed increased retention in the insoluble fraction in the CII RNAi line and vice versa. Immunolocalization revealed that both CI and CII sHSPs were present in cytosolic foci, some of which colocalized with HSP101 and with eEF1Bγ and eEF1Bß. Thus, CI and CII sHSPs have both unique and overlapping functions and act either directly or indirectly to protect specific translation factors in cytosolic stress granules.

An unusual dimeric small heat shock protein provides insight into the mechanism of this class of chaperones.

Small heat shock proteins (sHSPs) are virtually ubiquitous stress proteins that are also found in many normal tissues and accumulate in diseases of protein folding. They generally act as ATP-independent chaperones to bind and stabilize denaturing proteins that can be later reactivated by ATP-dependent Hsp70/DnaK, but the mechanism of substrate capture by sHSPs remains poorly understood. A majority of sHSPs form large oligomers, a property that has been linked to their effective chaperone action. We describe AtHsp18.5 from Arabidopsis thaliana, demonstrating that it is dimeric and exhibits robust chaperone activity, which adds support to the model that suboligomeric sHSP forms are a substrate binding species. Notably, like oligomeric sHSPs, when bound to substrate, AtHsp18.5 assembles into large complexes, indicating that reformation of sHSP oligomeric contacts is not required for assembly of sHSP-substrate complexes. Monomers of AtHsp18.5 freely exchange between dimers but fail to coassemble in vitro with dodecameric plant cytosolic sHSPs, suggesting that AtHsp18.5 does not interact by coassembly with these other sHSPs in vivo. Data from controlled proteolysis and hydrogen-deuterium exchange coupled with mass spectrometry show that the N- and C-termini of AtHsp18.5 are highly accessible and lack stable secondary structure, most likely a requirement for substrate interaction. Chaperone activity of a series of AtHsp18.5 truncation mutants confirms that the N-terminal arm is required for substrate protection and that different substrates interact differently with the N-terminal arm. In total, these data imply that the core α-crystallin domain of the sHSPs is a platform for flexible arms that capture substrates to maintain their solubility.

Dissecting heterogeneous molecular chaperone complexes using a mass spectrum deconvolution approach.

Small heat-shock proteins (sHSPs) are molecular chaperones that prevent irreversible aggregation through binding nonnative target proteins. Due to their heterogeneity, these sHSP:target complexes remain poorly understood. We present a nanoelectrospray mass spectrometry analysis algorithm for estimating the distribution of stoichiometries comprising a polydisperse ensemble of oligomers. We thus elucidate the organization of complexes formed between sHSPs and different target proteins. We find that binding is mass dependent, with the resultant complexes reflecting the native quaternary architecture of the target, indicating that protection happens early in the denaturation. Our data therefore explain the apparent paradox of how variable complex morphologies result from the generic mechanism of protection afforded by sHSPs. Our approach is applicable to a range of polydisperse proteins and provides a means for the automated and accurate interpretation of mass spectra derived from heterogeneous protein assemblies.

Small heat shock proteins and α-crystallins: dynamic proteins with flexible functions.

The small heat shock proteins (sHSPs) and the related α-crystallins (αCs) are virtually ubiquitous proteins that are strongly induced by a variety of stresses, but that also function constitutively in multiple cell types in many organisms. Extensive research has demonstrated that a majority of sHSPs and αCs can act as ATP-independent molecular chaperones by binding denaturing proteins and thereby protecting cells from damage due to irreversible protein aggregation. As a result of their diverse evolutionary history, their connection to inherited human diseases, and their novel protein dynamics, sHSPs and αCs are of significant interest to many areas of biology and biochemistry. However, it is increasingly clear that no single model is sufficient to describe the structure, function or mechanism of action of sHSPs and αCs. In this review, we discuss recent data that provide insight into the variety of structures of these proteins, their dynamic behavior, how they recognize substrates, and their many possible cellular roles.

The quaternary organization and dynamics of the molecular chaperone HSP26 are thermally regulated.

The function of ScHSP26 is thermally controlled: the heat shock that causes the destabilization of target proteins leads to its activation as a molecular chaperone. We investigate the structural and dynamical properties of ScHSP26 oligomers through a combination of multiangle light scattering, fluorescence spectroscopy, NMR spectroscopy, and mass spectrometry. We show that ScHSP26 exists as a heterogeneous oligomeric ensemble at room temperature. At heat-shock temperatures, two shifts in equilibria are observed: toward dissociation and to larger oligomers. We examine the quaternary dynamics of these oligomers by investigating the rate of exchange of subunits between them and find that this not only increases with temperature but proceeds via two separate processes. This is consistent with a conformational change of the oligomers at elevated temperatures which regulates the disassembly rates of this thermally activated protein.

Mechanistic differences between two conserved classes of small heat shock proteins found in the plant cytosol.

The small heat shock proteins (sHSPs) and alpha-crystallins are highly effective, ATP-independent chaperones that can bind denaturing client proteins to prevent their irreversible aggregation. One model of sHSP function suggests that the oligomeric sHSPs are activated to the client-binding form by dissociation at elevated temperatures to dimers or other sub-oligomeric species. Here we examine this model in a comparison of the oligomeric structure and chaperone activity of two conserved classes of cytosolic sHSPs in plants, the class I (CI) and class II (CII) proteins. Like the CI sHSPs, recombinant CII sHSPs from three divergent plant species, pea, wheat, and Arabidopsis, are dodecamers as determined by nano-electrospray mass spectrometry. While at 35 to 45 degrees C, all three CI sHSPs reversibly dissociate to dimers, the CII sHSPs retain oligomeric structure at high temperature. The CII dodecamers are, however, dynamic and rapidly exchange subunits, but unlike CI sHSPs, the exchange unit appears larger than a dimer. Differences in dodecameric structure are also reflected in the fact that the CII proteins do not hetero-oligomerize with CI sHSPs. Binding of the hydrophobic probe bis-ANS and limited proteolysis demonstrate CII proteins undergo significant, reversible structural changes at high temperature. All three recombinant CII proteins more efficiently protect firefly luciferase from insolubilization during heating than do the CI proteins. The CI and CII proteins behave strictly additively in client protection. In total, the results demonstrate that different sHSPs can achieve effective protection of client proteins by varied mechanisms.

Quaternary dynamics and plasticity underlie small heat shock protein chaperone function.

Small Heat Shock Proteins (sHSPs) are a diverse family of molecular chaperones that prevent protein aggregation by binding clients destabilized during cellular stress. Here we probe the architecture and dynamics of complexes formed between an oligomeric sHSP and client by employing unique mass spectrometry strategies. We observe over 300 different stoichiometries of interaction, demonstrating that an ensemble of structures underlies the protection these chaperones confer to unfolding clients. This astonishing heterogeneity not only makes the system quite distinct in behavior to ATP-dependent chaperones, but also renders it intractable by conventional structural biology approaches. We find that thermally regulated quaternary dynamics of the sHSP establish and maintain the plasticity of the system. This extends the paradigm that intrinsic dynamics are crucial to protein function to include equilibrium fluctuations in quaternary structure, and suggests they are integral to the sHSPs' role in the cellular protein homeostasis network.

Insights into small heat shock protein and substrate structure during chaperone action derived from hydrogen/deuterium exchange and mass spectrometry.

Small heat shock proteins (sHSPs) and the related alpha-crystallins are ubiquitous chaperones linked to neurodegenerative diseases, myopathies, and cataract. To better define their mechanism of chaperone action, we used hydrogen/deuterium exchange and mass spectrometry (HXMS) to monitor conformational changes during complex formation between the structurally defined sHSPs, pea PsHsp18.1, and wheat TaHsp16.9, and the heat-denatured model substrates malate dehydrogenase (MDH) and firefly luciferase. Remarkably, we found that even when complexed with substrate, the highly dynamic local structure of the sHSPs, especially in the N-terminal arm (>70% exchange in 5 s), remains unchanged. These results, coupled with sHSP-substrate complex stability, indicate that sHSPs do not adopt new secondary structure when binding substrate and suggest sHSPs are tethered to substrate at multiple sites that are locally dynamic, a feature that likely facilitates recognition and refolding of sHSP-bound substrate by the Hsp70/DnaK chaperone system. Both substrates were found to be stabilized in a partially unfolded state that is observed only in the presence of sHSP. Furthermore, peptide-level HXMS showed MDH was substantially protected in two core regions (residues 95-156 and 228-252), which overlap with the MDH structure protected in the GroEL-bound MDH refolding intermediate. Significantly, despite differences in the size and structure of TaHsp16.9-MDH and PsHsp18.1-MDH complexes, peptide-level HXMS patterns for MDH in both complexes are virtually identical, indicating that stabilized MDH thermal unfolding intermediates are not determined by the identity of the sHSP.