Focal adhesions are foci for tyrosine-based signal transduction via GIV/Girdin and G proteins.

GIV/Girdin is a multimodular signal transducer and a bona fide metastasis-related protein. As a guanidine exchange factor (GEF), GIV modulates signals initiated by growth factors (chemical signals) by activating the G protein Gαi. Here we report that mechanical signals triggered by the extracellular matrix (ECM) also converge on GIV-GEF via β1 integrins and that focal adhesions (FAs) serve as the major hubs for mechanochemical signaling via GIV. GIV interacts with focal adhesion kinase (FAK) and ligand-activated β1 integrins. Phosphorylation of GIV by FAK enhances PI3K-Akt signaling, the integrity of FAs, increases cell-ECM adhesion, and triggers ECM-induced cell motility. Activation of Gαi by GIV-GEF further potentiates FAK-GIV-PI3K-Akt signaling at the FAs. Spatially restricted signaling via tyrosine phosphorylated GIV at the FAs is enhanced during cancer metastasis. Thus GIV-GEF serves as a unifying platform for integration and amplification of adhesion (mechanical) and growth factor (chemical) signals during cancer progression

Structural basis for activation of trimeric Gi proteins by multiple growth factor receptors via GIV/Girdin.

A long-standing issue in the field of signal transduction is to understand the cross-talk between receptor tyrosine kinases (RTKs) and heterotrimeric G proteins, two major and distinct signaling hubs that control eukaryotic cell behavior. Although stimulation of many RTKs leads to activation of trimeric G proteins, the molecular mechanisms behind this phenomenon remain elusive. We discovered a unifying mechanism that allows GIV/Girdin, a bona fide metastasis-related protein and a guanine-nucleotide exchange factor (GEF) for Gαi, to serve as a direct platform for multiple RTKs to activate Gαi proteins. Using a combination of homology modeling, protein-protein interaction, and kinase assays, we demonstrate that a stretch of ∼110 amino acids within GIV C-terminus displays structural plasticity that allows folding into a SH2-like domain in the presence of phosphotyrosine ligands. Using protein-protein interaction assays, we demonstrated that both SH2 and GEF domains of GIV are required for the formation of a ligand-activated ternary complex between GIV, Gαi, and growth factor receptors and for activation of Gαi after growth factor stimulation. Expression of a SH2-deficient GIV mutant (Arg 1745→Leu) that cannot bind RTKs impaired all previously demonstrated functions of GIV-Akt enhancement, actin remodeling, and cell migration. The mechanistic and structural insights gained here shed light on the long-standing questions surrounding RTK/G protein cross-talk, set a novel paradigm, and characterize a unique pharmacological target for uncoupling GIV-dependent signaling downstream of multiple oncogenic RTKs

Activation of G proteins by GIV-GEF is a pivot point for insulin resistance and sensitivity.

Insulin resistance (IR) is a metabolic disorder characterized by impaired insulin signaling and cellular glucose uptake. The current paradigm for insulin signaling centers upon the insulin receptor (InsR) and its substrate IRS1; the latter is believed to be the sole conduit for postreceptor signaling. Here we challenge that paradigm and show that GIV/Girdin, a guanidine exchange factor (GEF) for the trimeric G protein Gαi, is another major hierarchical conduit for the metabolic insulin response. By virtue of its ability to directly bind InsR, IRS1, and phosphoinositide 3-kinase, GIV serves as a key hub in the immediate postreceptor level, which coordinately enhances the metabolic insulin response and glucose uptake in myotubes via its GEF function. Site-directed mutagenesis or phosphoinhibition of GIV-GEF by the fatty acid/protein kinase C-theta pathway triggers IR. Insulin sensitizers reverse phosphoinhibition of GIV and reinstate insulin sensitivity. We also provide evidence for such reversible regulation of GIV-GEF in skeletal muscles from patients with IR. Thus GIV is an essential upstream component that couples InsR to G-protein signaling to enhance the metabolic insulin response, and impairment of such coupling triggers IR. We also provide evidence that GIV-GEF serves as therapeutic target for exogenous manipulation of physiological insulin response and reversal of IR in skeletal muscles

Daple is a novel non-receptor GEF required for trimeric G protein activation in Wnt signaling

Peer reviewedPublisher PD

Plasminogen Activator Inhibitor-1 in Cigarette Smoke Exposure and Influenza A Virus Infection-Induced Lung Injury

Parenchymal lung inflammation and airway and alveolar epithelial cell apoptosis are associated with cigarette smoke exposure (CSE), which contributes to chronic obstructive pulmonary disease (COPD). Epidemiological studies indicate that people exposed to chronic cigarette smoke with or without COPD are more susceptible to influenza A virus (IAV) infection. We found increased p53, PAI-1 and apoptosis in AECs, with accumulation of macrophages and neutrophils in the lungs of patients with COPD. In Wild-type (WT) mice with passive CSE (PCSE), p53 and PAI-1 expression and apoptosis were increased in AECs as was lung inflammation, while those lacking p53 or PAI-1 resisted AEC apoptosis and lung inflammation. Further, inhibition of p53-mediated induction of PAI-1 by treatment of WT mice with caveolin-1 scaffolding domain peptide (CSP) reduced PCSE-induced lung inflammation and reversed PCSE-induced suppression of eosinophil-associated RNase1 (EAR1). Competitive inhibition of the p53-PAI-1 mRNA interaction by expressing p53-binding 3\u27UTR sequences of PAI-1 mRNA likewise suppressed CS-induced PAI-1 and AEC apoptosis and restored EAR1 expression. Consistent with PCSE-induced lung injury, IAV infection increased p53, PAI-1 and apoptosis in AECs in association with pulmonary inflammation. Lung inflammation induced by PCSE was worsened by subsequent exposure to IAV. Mice lacking PAI-1 that were exposed to IAV showed minimal viral burden based on M2 antigen and hemagglutination analyses, whereas transgenic mice that overexpress PAI-1 without PCSE showed increased M2 antigen and inflammation after IAV infection. These observations indicate that increased PAI-1 expression promotes AEC apoptosis and exacerbates lung inflammation induced by IAV following PCSE

To determine the prognostic accuracy of the HEART score as a predictor for major adverse cardiac events in patients presenting with chest pain to emergency department in a tertiary care hospital

INTRODUCTION: One of the main causes of sudden cardiac death in the emergency department is myocardial infarction. Although there are several scores that helped predict an identified acute coronary incident, there was no quantitative tool available to risk stratifying patients with chest pain to support more decisions. The study is aimed to determine the prognostic accuracy of the HEART score as a predictor for major adverse cardiac events in patients presenting with chest pain to the emergency medicine department (ED). MATERIAL AND METHODS: Study included 83 adult patients presenting with Acute Myocardial Infarction who had chest pain attending to the ED were studied their HEART score to predict major adverse cardiac events. RESULTS: 60.24% of males and 39.76% of females with mean age of 57.83 ± 12.85 years were presented to ED. 44.56% had hypertension, 46.99% of diabetes mellitus, 21.69% of smoking, 16.87% of alcoholism, 4.82% of obesity, and 3.61% of patients with family history of cardiac diseases. 28.92% had non-specific repolarization, and 33.73% of patients had significant ST-Depression. According to Heart score, 26.51% of patients had low risk, 39.76% of patients had moderate risk, and 33.73% of patients had high risk. More percentage of male patient’s (67.9%) were in the high risk group of heart score than females (32.1%). ST-Depression cases were more in the high risk group (85.7%), and statistical significant association seen between ECG and the heart score (P<0.0001). among risk factors, Hypertension and Diabetes mellitus patients was more in the high risk groups with 48.6%, and 53.8% (P=0.001). 100% of high risk cases had ≥3 x normal limit of troponin, and there was a statistically association seen between troponin and heart score (P<0.0001). Diagnosis of HEART score of the low risk group showed that the risk factor had significantly higher AUC value (AUC = 0.801) than the age group (AUC = 0.778), history (AUC = 0.747), Troponin (AUC = 0.738), and ECG (AUC = 0.722). Out of 22 cases of the low risk group, 6 of Unstable angina (UA), 16 of NSTEMI, 4 of Percutaneous coronary intervention (PCI), 2 CABG, and 1 cardiovascular (CV) death. For moderate risk group (n=33), 13 of UA, 17 of NSTEMI, 3 of STEMI, 20 of PCI, 14 of CABG, and 12 of CV deaths. For high risk group (n=28), 10 UA, 14 of NSTEMI, 3 of STEMI, 9 of PCI, 6 of CABG, and 4 number of CV death. CONCLUSIONS: It was concluded that the HEART score should be used as the primary clinical decision tool for the risk stratification and a good predictor of major adverse cardiac events in patients presenting with chest pain to the emergency department to promote their safe and efficient nature in a community hospital setting