Systems Biology of the Vasopressin V2 Receptor: New Tools for Discovery of Molecular Actions of a GPCR.

Systems biology can be defined as the study of a biological process in which all of the relevant components are investigated together in parallel to discover the mechanism. Although the approach is not new, it has come to the forefront as a result of genome sequencing projects completed in the first few years of the current century. It has elements of large-scale data acquisition (chiefly next-generation sequencing-based methods and protein mass spectrometry) and large-scale data analysis (big data integration and Bayesian modeling). Here we discuss these methodologies and show how they can be applied to understand the downstream effects of GPCR signaling, specifically looking at how the neurohypophyseal peptide hormone vasopressin, working through the V2 receptor and PKA activation, regulates the water channel aquaporin-2. The emerging picture provides a detailedframework for understanding the molecular mechanisms involved in water balance disorders, pointing the way to improved treatment of both polyuric disorders and water-retention disorders causing dilutional hyponatremia.

Data resource: vasopressin-regulated protein phosphorylation sites in the collecting duct.

Vasopressin controls renal water excretion through actions to regulate aquaporin-2 (AQP2) trafficking, transcription, and degradation. These actions are in part dependent on vasopressin-induced phosphorylation changes in collecting duct cells. Although most efforts have focused on the phosphorylation of AQP2 itself, phosphoproteomic studies have identified many vasopressin-regulated phosphorylation sites in proteins other than AQP2. The goal of this bioinformatics-based review is to create a compendium of vasopressin-regulated phosphorylation sites with a focus on those that are seen in both native rat inner medullary collecting ducts and cultured collecting duct cells from the mouse (mpkCCD), arguing that these sites are the best candidates for roles in AQP2 regulation. This analysis identified 51 vasopressin-regulated phosphorylation sites in 45 proteins. We provide resource web pages at https://esbl.nhlbi.nih.gov/Databases/AVP-Phos/ and https://esbl.nhlbi.nih.gov/AVP-Network/, listing the phosphorylation sites and describing annotated functions of each of the vasopressin-targeted phosphoproteins. Among these sites are 23 consensus protein kinase A (PKA) sites that are increased in response to vasopressin, consistent with a central role for PKA in vasopressin signaling. The remaining sites are predicted to be phosphorylated by other kinases, most notably ERK1/2, which accounts for decreased phosphorylation at sites with a X-p(S/T)-P-X motif. Additional protein kinases that undergo vasopressin-induced changes in phosphorylation are Camkk2, Cdk18, Erbb3, Mink1, and Src, which also may be activated directly or indirectly by PKA. The regulated phosphoproteins are mapped to processes that hypothetically can account for vasopressin-mediated control of AQP2 trafficking, cytoskeletal alterations, and Aqp2 gene expression, providing grist for future studies.NEW & NOTEWORTHY Vasopressin regulates renal water excretion through control of the aquaporin-2 water channel in collecting duct cells. Studies of vasopressin-induced protein phosphorylation have focused mainly on the phosphorylation of aquaporin-2. This study describes 44 phosphoproteins other than aquaporin-2 that undergo vasopressin-mediated phosphorylation changes and summarizes potential physiological roles of each.

Proteomics and AQP2 regulation.

The advent of modern quantitative protein mass spectrometry techniques around the turn of the 21st century has contributed to a revolution in biology referred to as 'systems biology'. These methods allow identification and quantification of thousands of proteins in a biological specimen, as well as detection and quantification of post-translational protein modifications including phosphorylation. Here, we discuss these methodologies and show how they can be applied to understand the effects of the peptide hormone vasopressin to regulate the molecular water channel aquaporin-2. The emerging picture provides a detailed framework for understanding the molecular mechanisms involved in water balance disorders.

Quantitative Proteomics of Medium-Sized Extracellular Vesicle-Enriched Plasma of Lacunar Infarction for the Discovery of Prognostic Biomarkers.

Lacunar infarction (LACI), a subtype of acute ischemic stroke, has poor mid- to long-term prognosis due to recurrent vascular events or incident dementia which is difficult to predict using existing clinical data. Herein, we aim to discover blood-based biomarkers for LACI as a complementary prognostic tool. Convalescent plasma was collected from forty-five patients following a non-disabling LACI along with seventeen matched control subjects. The patients were followed up prospectively for up to five years to record an occurrence of adverse outcome and grouped accordingly (i.e., LACI-no adverse outcome, LACI-recurrent vascular event, and LACI-cognitive decline without any recurrence of vascular events). Medium-sized extracellular vesicles (MEVs), isolated from the pooled plasma of four groups, were analyzed by stable isotope labeling and 2D-LC-MS/MS. Out of 573 (FDR < 1%) quantified proteins, 146 showed significant changes in at least one LACI group when compared to matched healthy control. A systems analysis revealed that major elements (~85%) of the MEV proteome are different from the proteome of small-sized extracellular vesicles obtained from the same pooled plasma. The altered MEV proteins in LACI patients are mostly reduced in abundance. The majority of the shortlisted MEV proteins are not linked to commonly studied biological processes such as coagulation, fibrinolysis, or inflammation. Instead, they are linked to oxygen-glucose deprivation, endo-lysosomal trafficking, glucose transport, and iron homeostasis. The dataset is provided as a web-based data resource to facilitate meta-analysis, data integration, and targeted large-scale validation.

Phosphoproteomic Identification of Vasopressin/cAMP/Protein Kinase A-Dependent Signaling in Kidney.

Water excretion by the kidney is regulated by the neurohypophyseal peptide hormone vasopressin through actions in renal collecting duct cells to regulate the water channel protein aquaporin-2. Vasopressin signaling is initiated by binding to a G-protein-coupled receptor called V2R, which signals through heterotrimeric G-protein subunit Gs α, adenylyl cyclase 6, and activation of the cAMP-regulated protein kinase (PKA). Signaling events coupling PKA activation and aquaporin-2 regulation were largely unknown until the advent of modern protein mass spectrometry techniques that allow proteome-wide quantification of protein phosphorylation changes (phosphoproteomics). This short review documents phosphoproteomic findings in collecting duct cells describing the response to V2R-selective vasopressin agonists and antagonists, the response to CRISPR-mediated deletion of PKA, results from in vitro phosphorylation studies using recombinant PKA, the response to the broad-spectrum kinase inhibitor H89 (N-[2-p-bromocinnamylamino-ethyl]-5-isoquinolinesulphonamide), and the responses underlying lithium-induced nephrogenic diabetes insipidus. These phosphoproteomic data sets have been made available online for modeling vasopressin signaling and signaling downstream from other G-protein-coupled receptors. SIGNIFICANCE STATEMENT: New developments in protein mass spectrometry are facilitating progress in identification of signaling networks. Using mass spectrometry, it is now possible to identify and quantify thousands of phosphorylation sites in a given cell type (phosphoproteomics). The authors describe the use of phosphoproteomics technology to identify signaling mechanisms downstream from a G-protein-coupled receptor, the vasopressin V2 subtype receptor, and its role of the regulation and dysregulation of water excretion in the kidney. Data from multiple phosphoproteomic data sets are provided as web-based resources.

PKA-independent vasopressin signaling in renal collecting duct.

Vasopressin regulates renal water excretion by binding to a Gα s-coupled receptor (V2R) in collecting duct cells, resulting in increased water permeability through regulation of the aquaporin-2 (AQP2) water channel. This action is widely accepted to be associated with cAMP-mediated activation of protein kinase A (PKA). Here, we use phosphoproteomics in collecting duct cells in which PKA has been deleted (CRISPR-Cas9) to identify PKA-independent responses to vasopressin. The results show that V2R-mediated vasopressin signaling is predominantly, but not entirely, PKA-dependent. Upregulated sites in PKA-null cells include Ser256 of AQP2, which is critical to regulation of AQP2 trafficking. In addition, phosphorylation changes in the protein kinases Stk39 (SPAK) and Prkci (an atypical PKC) are consistent with PKA-independent regulation of these protein kinases. Target motif analysis of the phosphopeptides increased in PKA-null cells indicates that vasopressin activates one or more members of the AMPK/SNF1-subfamily of basophilic protein kinases. In vitro phosphorylation assays using recombinant, purified SNF1-subfamily kinases confirmed postulated target specificities. Of interest, measured IBMX-dependent cAMP levels were an order of magnitude higher in PKA-null than in PKA-intact cells, indicative of a PKA-dependent feedback mechanism. Overall, the findings support the conclusion that V2-receptor mediated signaling in collecting duct cells is in part PKA-independent.

Control of filament length by a depolymerizing gradient.

Cells assemble microns-long filamentous structures from protein monomers that are nanometers in size. These structures are often highly dynamic, yet in order for them to function properly, cells maintain them at a precise length. Here we investigate length-dependent depolymerization as a mechanism of length control. This mechanism has been recently proposed for flagellar length control in the single cell organisms Chlamydomonas and Giardia. Length dependent depolymerization can arise from a concentration gradient of a depolymerizing protein, such as kinesin-13 in Giardia, along the length of the flagellum. Two possible scenarios are considered: a linear and an exponential gradient of depolymerizing proteins. We compute analytically the probability distributions of filament lengths for both scenarios and show how these distributions are controlled by key biochemical parameters through a dimensionless number that we identify. In Chlamydomonas cells, the assembly dynamics of its two flagella are coupled via a shared pool of molecular components that are in limited supply, and so we investigate the effect of a limiting monomer pool on the length distributions. Finally, we compare our calculations to experiments. While the computed mean lengths are consistent with observations, the noise is two orders of magnitude smaller than the observed length fluctuations.

BOX engineering to mitigate negative differential resistance in MFIS negative capacitance FDSOI FET: an analog perspective.

Till date, the existing understanding of negative differential resistance (NDR) is obtained from metal-ferro-metal-insulator-semiconductor (MFMIS) FET, and it has been utilized for both MFMIS and metal-ferro-insulator-semiconductor (MFIS) based NCFETs. However, in MFIS architecture, the ferroelectric capacitance (CFE) is not a lumped capacitance. Therefore, for MFIS negative capacitance (NC) devices, the physical explanation which governs the NDR mechanism needs to be addressed. In this work, for the first time, we present the first principle explanation of the NDR effect in MFIS NC FDSOI. We found that the output current variation with the drain to source voltage (VDS), (i.e.gds) primarily depends upon two parameters: (a)VDSdependent inversion charge gradient (∂n/∂VDS); (b)VDSsensitive electron velocity (∂v/∂VDS), and the combined effect of these two dependencies results in NDR. Further, to mitigate the NDR effect, we proposed the BOX engineered NC FDSOI FET, in which the buried oxide (BOX) layer is subdivided into the ferroelectric (FE) layer and the SiO2layer. In doing so, the inversion charge in the channel is enhanced by the BOX engineered FE layer, which in turn mitigates the NDR and a nearly zerogdswith a minimal positive slope has been obtained. Through well-calibrated TCAD simulations, by utilizing the obtained positivegds, we also designed aVDSindependent constant current mirror which is an essential part of analog circuits. Furthermore, we discussed the impact of the FE parameter (remanent polarization and coercive field) variation on the device performances. We have also compared the acquired results with existing literature on NC-based devices, which justifies that our proposed structure exhibits complete diminution of NDR, thus enabling its use in analog circuit design.

Phosphoproteomic identification of vasopressin V2 receptor-dependent signaling in the renal collecting duct.

Vasopressin controls water balance largely through PKA-dependent effects to regulate the collecting duct water channel aquaporin-2 (AQP2). Although considerable information has accrued regarding the regulation of water and solute transport in collecting duct cells, information is sparse regarding the signaling connections between PKA and transport responses. Here, we exploited recent advancements in protein mass spectrometry to perform a comprehensive, multiple-replicate analysis of changes in the phosphoproteome of native rat inner medullary collecting duct cells in response to the vasopressin V2 receptor-selective agonist 1-desamino-8D-arginine vasopressin. Of the 10,738 phosphopeptides quantified, only 156 phosphopeptides were significantly increased in abundance, and only 63 phosphopeptides were decreased, indicative of a highly selective response to vasopressin. The list of upregulated phosphosites showed several general characteristics: 1) a preponderance of sites with basic (positively charged) amino acids arginine (R) and lysine (K) in position -2 and -3 relative to the phosphorylated amino acid, consistent with phosphorylation by PKA and/or other basophilic kinases; 2) a greater-than-random likelihood of sites previously demonstrated to be phosphorylated by PKA; 3) a preponderance of sites in membrane proteins, consistent with regulation by membrane association; and 4) a greater-than-random likelihood of sites in proteins with class I COOH-terminal PDZ ligand motifs. The list of downregulated phosphosites showed a preponderance of those with proline in position +1 relative to the phosphorylated amino acid, consistent with either downregulation of proline-directed kinases (e.g., MAPKs or cyclin-dependent kinases) or upregulation of one or more protein phosphatases that selectively dephosphorylate such sites (e.g., protein phosphatase 2A). The phosphoproteomic data were used to create a web resource for the investigation of G protein-coupled receptor signaling and regulation of AQP2-mediated water transport.

Evaluation of the effect of trypsin digestion buffers on artificial deamidation.

Nonenzymatic deamidation occurs readily under the condition of trypsin digestion, resulting in the identification of many artificial deamidation sites. To evaluate the effect of trypsin digestion buffers on artificial deamidation, we compared the three commonly used buffers Tris-HCl (pH 8), ammonium bicarbonate (ABC), and triethylammonium bicarbonate (TEAB), and ammonium acetate (pH 6), which was reported to reduce Asn deamidation. iTRAQ quantification on rat kidney tissue digested in these four buffers indicates that artificial Asn deamidation is produced in the order of ammonium acetate < Tris-HCl < ABC < TEAB, and Gln deamidation has no significant differences in all tested buffers. Label-free experiments show the same trend, while protein and unique peptide identification are comparable using these four buffers. To explain the differences of these four buffers in producing artificial Asn deamidation, we determined the half-life of Asn deamidation in these buffers using synthetic peptides containing -Asn-Gly- sequences. It is 51.4 ± 6.0 days in 50 mM of ammonium acetate (pH 6) at 37 °C, which is about 23, 104, and 137 times that in Tris-HCl, ABC, and TEAB buffers, respectively. In conclusion, ammonium acetate (pH 6) is more suitable than other tested buffers for characterizing endogenous deamidation and N-glycosylation.

Evidence for a functional thymic stromal lymphopoietin signaling axis in fibrotic lung disease.

Thymic stromal lymphopoietin (TSLP) recently has emerged as a key cytokine in the development of type 2 immune responses. Although traditionally associated with allergic inflammation, type 2 responses are also recognized to contribute to the pathogenesis of tissue fibrosis. However, the role of TSLP in the development of non-allergen-driven diseases, characterized by profibrotic type 2 immune phenotypes and excessive fibroblast activation, remains underexplored. Fibroblasts represent the key effector cells responsible for extracellular matrix production but additionally play important immunoregulatory roles, including choreographing immune cell recruitment through chemokine regulation. The aim of this study was to examine whether TSLP may be involved in the pathogenesis of a proto-typical fibrotic disease, idiopathic pulmonary fibrosis (IPF). We combined the immunohistochemical analysis of human IPF biopsy material with signaling studies by using cultured primary human lung fibroblasts and report for the first time, to our knowledge, that TSLP and its receptor (TSLPR) are highly upregulated in IPF. We further show that lung fibroblasts represent both a novel cellular source and target of TSLP and that TSLP induces fibroblast CCL2 release (via STAT3) and subsequent monocyte chemotaxis. These studies extend our understanding of TSLP as a master regulator of type 2 immune responses beyond that of allergic inflammatory conditions and suggest a novel role for TSLP in the context of chronic fibrotic lung disease.

Congenital giant right atrium in an elderly woman.

Enlargement of right atrium is usually secondary to pulmonary hypertension due to valvular heart diseases or obstructive pulmonary disorders, atrial septal defect, tricuspid atresia or stenosis, pulmonary stenosis, primary pulmonary hypertension, Ebstein's anomaly. Congenital enlargement of right atrium is rare and it commonly presents in children. Our patient presented with congenital giant right atrium at 65 years of age, other cardiac diseases being excluded. Patient developed tricuspid regurgitation, but pulmonary hypertension was absent till the date. Congenital giant right atrium has rarely been reported from India.

Ex vivo micro-computed tomography analysis of bleomycin-induced lung fibrosis for preclinical drug evaluation.

Research into the pathogenesis underlying the development of idiopathic pulmonary fibrosis is hampered by a repertoire of animal models that fail to recapitulate all the features of the human disease. Better use and understanding of what the animal models represent may improve clinical predictability. We interrogated ex vivo micro-computed tomography (CT) as a novel end-point measure in the mouse model of bleomycin-induced lung fibrosis (BILF), and to evaluate a therapeutic dosing regimen for preclinical drug evaluation. A detailed characterisation of BILF was performed using standard end-point measures (lung hydroxyproline and histology). High resolution micro-CT (∼13.7 µm voxel size) was evaluated for quantifying the extent and severity of lung fibrosis. The period from 14 to 28 days following bleomycin instillation represents progression of established fibrosis. A therapeutic dosing regimen during this period was validated using a transforming growth factor-ß receptor-1 kinase inhibitor, and micro-CT provided a highly sensitive and quantitative measure of fibrosis. Moreover, fibrotic lesions did not completely resolve, but instead persisted for ≥6 months following a single insult with bleomycin. Ex vivo micro-CT analysis of BILF allows robust evaluation of therapeutic dosing once fibrosis is already well established, requiring fewer mice than conventional biochemical end-points.

Resilience and its relationship with disability in persons with bipolar disorder and schizophrenia: A comparative study.

Background: Resilience is the capacity to bounce back from adversity. Severe mental illnesses are associated with poor and heterogeneous functional outcomes. Symptom remission is inadequate to achieve patient-oriented outcome, and positive psychopathology constructs like resilience have emerged as possible mediators. An exploration of resilience and its association with functional outcomes can drive therapeutic endeavors. Aim: To assess and compare the influence of resilience on disability among patients diagnosed and treated for bipolar disorder and schizophrenia in a tertiary care facility. Methods: Study design - Hospital-based, cross-sectional, comparative design; study population - patients of bipolar disorder and schizophrenia with 2-5 years illness and Clinical Global Impression - Severity (CGI-S) <4; sampling procedure - consecutive sampling; sample size - 30 patients each; scales used - Connor-Davidson Resilience Scale (CD-RISC), Indian Disability Evaluation and Assessment Scale (IDEAS), and CGI-S; patients were evaluated with IDEAS, and 15 persons with and without a significant disability were recruited in each group of schizophrenia and bipolar disorder. Results: The mean CD-RISC 25 score for persons with schizophrenia was 73.60 ± 13.87, whereas that for persons with bipolar disorder was 78.10 ± 15.26. For schizophrenia, only CDRISC-25 scores are statistically significant (t = -2.582, P = 0.018) for predicting IDEAS global disability. For bipolar disorder, CDRISC-25 scores (t = -2.977, P = 0.008) and CGI-severity scores (t = 3.135, P = 0.005) are statistically significant for predicting IDEAS global disability. Conclusion: When disability is factored in, resilience is comparable in persons with schizophrenia and bipolar disorder. Resilience independently predicts disability in both groups. However, the type of disorder does not significantly affect the relationship between resilience and disability. Irrespective of diagnosis, higher resilience is associated with lower disability.

GaAs based long-wavelength microring resonator optical switches utilising bias assisted carrier-injection induced refractive index change.

We propose and analyse a GaAs-based optical switch having a ring resonator configuration which can switch optical telecommunication signals over the 1300 nm and 1500 nm bands, using bias assisted carrier injection as the switching mechanism. The switching is achieved through variation in the refractive index of the ring resonator produced by changing the injected carrier density through the application of bias voltage. Detail analysis of the switching characteristics reveals that the amount of switching depends on the refractive index change, which indeed is a strong function of injected carrier density and applied bias voltage. An isolation of 25 dB can be achieved during the ON state, while more than 40 dB isolation is realised during the OFF state. More importantly, our analysis shows that the proposed GaAs-based switch can operate over the 1300 nm and 1500 nm optical telecommunication bands, that are much farther from the bandgap of the GaAs material, without the need for "conventional" Indium based ternary and quaternary semiconductor materials. It therefore extends the usable wavelength of GaAs based optoelectronic devices. Furthermore, we have presented detail calculations to quantify power-delay metric of the proposed device. The proposed optical switch maintains a smaller footprint as when compared to Mach-Zehnder Interferometer or Directional Coupler based switches therefore, making it suitable for large scale integration and implementing next generation optical interconnects, optical communication and computing.

Hypoxic tumor cell modulates its microenvironment to enhance angiogenic and metastatic potential by secretion of proteins and exosomes.

Under hypoxia, tumor cells produce a secretion that modulates their microenvironment to facilitate tumor angiogenesis and metastasis. Here, we observed that hypoxic or reoxygenated A431 carcinoma cells exhibited enhanced angiogenic and metastatic potential such as reduced cell-cell and cell-extracellular matrix adhesion, increased invasiveness, and production of a secretion with increased chorioallantoic membrane angiogenic activity. Consistent with these observations, quantitative proteomics revealed that under hypoxia the tumor cells secreted proteins involved in angiogenesis, focal adhesion, extracellular matrix-receptor interaction, and immune cell recruitment. Unexpectedly, the secreted proteins were predominantly cytoplasmic and membrane proteins. Ultracentrifugation at 100,000 x g precipitated 54% of the secreted proteins and enriched for many exosome-associated proteins such as the tetraspanins and Alix and also proteins with the potential to facilitate angiogenesis and metastasis. Two tetraspanins, CD9 and CD81, co-immunoprecipitated. Together, these data suggested that tumor cells secrete proteins and exosomes with the potential to modulate their microenvironment and facilitate angiogenesis and metastasis.

Simultaneous characterization of glyco- and phosphoproteomes of mouse brain membrane proteome with electrostatic repulsion hydrophilic interaction chromatography.

Characterization of glyco- and phosphoproteins as well as their modification sites poses many challenges, the greatest being loss of their signals during mass spectrometric detection due to substoichiometric amounts and the ion suppression effect caused by peptides of high abundance. We report here an optimized protocol using electrostatic repulsion hydrophilic interaction chromatography for the simultaneous enrichment of glyco- and phosphopeptides from mouse brain membrane protein digest. With this protocol, we successfully identified 544 unique glycoproteins and 922 glycosylation sites, which were significantly higher than those from the commonly used hydrazide chemistry method (192 glycoproteins and 345 glycosylation sites). Moreover, a total of 383 phosphoproteins and 915 phosphorylation sites were recovered from the sample, suggesting that this protocol has the potential to enrich both glycopeptides and phosphopeptides simultaneously. Of the total 995 glycosylation sites identified from both methods, 96% were considered new as they were either annotated as putative or not documented in the newly released Swiss-Prot database. Thus, this study could be of significant value in complementing the current glycoprotein database and provides a unique opportunity to study the complex interaction of two different post-translational modifications in health and disease without being affected by interexperimental variations.

How to assemble a scale-invariant gradient.

Intracellular protein gradients serve a variety of functions, such as the establishment of cell polarity or to provide positional information for gene expression in developing embryos. Given that cell size in a population can vary considerably, for the protein gradients to work properly they often have to be scaled to the size of the cell. Here, we examine a model of protein gradient formation within a cell that relies on cytoplasmic diffusion and cortical transport of proteins toward a cell pole. We show that the shape of the protein gradient is determined solely by the cell geometry. Furthermore, we show that the length scale over which the protein concentration in the gradient varies is determined by the linear dimensions of the cell, independent of the diffusion constant or the transport speed. This gradient provides scale-invariant positional information within a cell, which can be used for assembly of intracellular structures whose size is scaled to the linear dimensions of the cell, such as the cytokinetic ring and actin cables in budding yeast cells.

In Vitro Oxygen Glucose Deprivation Model of Ischemic Stroke: A Proteomics-Driven Systems Biological Perspective.

Oxygen glucose deprivation (OGD) of brain cells is the commonest in vitro model of ischemic stroke that is used extensively for basic and preclinical stroke research. Protein mass spectrometry is one of the most promising and rapidly evolving technologies in biomedical research. A systems-level understanding of cell-type-specific responses to oxygen and glucose deprivation without systemic influence is a prerequisite to delineate the response of the neurovascular unit following ischemic stroke. In this systematic review, we summarize the proteomics studies done on different OGD models. These studies have followed an expression or interaction proteomics approach. They have been primarily used to understand the cellular pathophysiology of ischemia-reperfusion injury or to assess the efficacy of interventions as potential treatment options. We compile the limitations of OGD model and downstream proteomics experiment. We further show that despite having limitations, several proteins shortlisted as altered in in vitro OGD-proteomics studies showed comparable regulation in ischemic stroke patients. This showcases the translational potential of this approach for therapeutic target and biomarker discovery. We next discuss the approaches that can be adopted for cell-type-specific validation of OGD-proteomics results in the future. Finally, we briefly present the research questions that can be addressed by OGD-proteomics studies using emerging techniques of protein mass spectrometry. We have also created a web resource compiling information from OGD-proteomics studies to facilitate data sharing for community usage. This review intends to encourage preclinical stroke community to adopt a hypothesis-free proteomics approach to understand cell-type-specific responses following ischemic stroke.