Outcomes in Managing Vascular Tinnitus: Institutional Experience and Review of 6-Year Literature.

To evaluate the outcomes in patients of vascular tinnitus managed at our institute. The clinical data of all patients diagnosed with pulsatile tinnitus from January 2014 to April 2022 and managed at AIIMS, Bhubaneswar, was retrospectively reviewed. The diagnosis, treatment and outcomes were analyzed. A 6-year literature review was performed from March 2015 to April 2021. Our series discusses managing eleven cases of vascular tinnitus with varied aetiology and their outcomes. Out of the eleven cases, eight patients underwent surgical or radiological intervention, and seven had complete resolution of symptoms. Of the eleven patients, three had partial resolution. The 6-year literature review revealed sigmoid and transverse sinus as the most common causative anatomical sites for pulsatile tinnitus. Amongst those who received an intervention, 83.56% of the patients had complete resolution of symptoms. Vascular tinnitus can be cured if the exact vessel causing it is localized. Clinical suspicion is based on the character of tinnitus and patient history. A careful evaluation of the head and neck sites for any vascular anomaly that can cause pulsatile tinnitus must be done. Radiology demonstrates treatable causes of it. It delineates the aberrant anatomical variations that can lead to this disturbing aetiology. Treatable causes are best addressed, and pathology should be taken care of. A multidisciplinary team comprising ENT surgeons, audiologists and interventional radiologists must identify and treat the pathology.

Posterior nasal nerve neurectomy for the treatment of chronic rhinosinusitis with nasal polyposis: a randomized controlled trial.

BACKGROUND: Managing Chronic Rhinosinusitis with Nasal Polyposis (CRSwNP) is always challenging due to the chronicity of the disease and its intractable course. Posterior nasal neurectomy (PNN) can be effective in alleviating symptoms of CRSwNP. MATERIALS AND METHODS: The study was conducted in a tertiary care referral hospital from August 2019 to April 2022. A total of 46 patients of CRSwNP were included (23 patients in the study and 23 in the control group). Patients in the study group underwent endoscopic sinus surgery (ESS) and PNN and patients in the control group with ESS. The symptoms and quality-of-life improvement were assessed at 1, 4, 12, and 24 weeks after the surgery. RESULTS: On intragroup analysis between the preoperative and postoperative scores (SNOT-22, RSDI and LK Score), we found a significant difference for each (p < 0.05). When the improvement of outcome scores was compared between the two groups, a significant difference was obtained for SNOT-22 and RSDI scores at 1 week and 4 weeks (p < 0.05). There was no significant difference found for the duration of surgery/complications between the two groups (p = 1.00). CONCLUSION: The PNN can be an effective add-on procedure in patients with CRSwNP in alleviating short-term control of the symptoms and the quality of life. A larger sample size with long-term follow-up may be required for a better understanding of the efficacy of the PNN in patients with CRSwNP.

To evaluate the efficacy of topical anti-fungal therapy in postoperative cases of COVID Associated Mucormycosis (CAM): A single-blinded randomized control trial.

PURPOSE: To compare the efficacy of 0.1 % w/w Liposomal Amphotericin-B gel with 10 % w/w Povidone-Iodine and saline nasal douching in preventing revision surgery in patients with CAM. STUDY DESIGN: Multi-arm, parallel randomized control trial. STUDY SETTING: The trial was conducted in the Department of ENT, All India Institute of Medical Sciences (AIIMS) Bhubaneswar. METHODS: Participants: Microbiologically and histologically proven cases of mucormycosis who underwent surgical debridement were included in the study. INTERVENTIONS: Postoperatively, patients were randomized into three groups based on the type of topical intervention received, in the form of Lipid-based Amphotericin B gel, povidone­iodine ointment or saline nasal douching. OUTCOME: Requirement of revision surgery in postoperative cases of CAM. RANDOMIZATION: Participants were allotted to one of the three arms by block randomization. BLINDING: Single-blinded trial. RESULTS: Numbers randomized: 15 participants were randomized to each group. Recruitment: Completed recruiting. Numbers analyzed: 15 participants were analyzed in each group. OUTCOMES: Control arm's risk of revision surgery was 4.50 (95 % CI: 1.16-17.44) times than Lipid-based Amphotericin B gel arm and 1.50 (95 % CI: 0.71-3.16) times that of the Povidone- Iodine arm. The difference was statistically significant (p = 0.02) for Amphotericin but not for Povidone-Iodine. CONCLUSIONS: Topical Amphotericin-B gel application in the postoperative cavity can decrease the need for revision surgery and help in early recovery. TRIAL REGISTRATION: CTRI/2021/10/037257. Clinical Trials Registry of India.

Efficacy of endoscopic repair for CSF otorrhoea in children with recurrent meningitis due to incomplete partition type 1.

OBJECTIVE: To review the efficacy of endoscopic management with or without cochlear implantation in a pediatric population presenting with recurrent meningitis due to inner ear incomplete partition type 1 (IP-1). MATERIALS AND METHODS: A multicentric report of 6 patients with a history of recurrent meningitis due to IP-1 was done. Radiological evaluation was performed to confirm the diagnosis. Transcanal endoscopic repair of the defect was performed in 3 cases, 2 cases underwent endoscope-assisted repair followed by cochlear implantation in the contralateral ear later, and 1 patient underwent endoscopic repair along with simultaneous cochlear implantation. RESULTS: Radiology confirmed the diagnosis and identified the site of the leak. A leak was detected in all cases from the stapes footplate. Two patients with unilateral deformity had a CSF-filled cyst protruding through a defect in the stapes footplate, and the rest of the four had a high flow CSF leak from the footplate. Five patients who underwent repair have had no further episodes of meningitis. One patient who received simultaneous implantation and repair developed postoperative meningitis managed successfully with antibiotics. CONCLUSION: Hearing loss due to inner ear deformity can be easily missed as a cause for recurrent meningitis, especially if unilateral. A high index of suspicion, audiological screening and radiology are essential to clinch the diagnosis. In such cases, a pure endoscopic or endoscopic assisted transcanal approach to repair CSF otorrhoea is an effective alternative to more radical procedures like subtotal petrosectomy with obliteration. In patients with bilateral profound hearing loss, simultaneous cochlear implantation and repair of the defect can be performed successfully.

The Host-Microbiome Response to Hyperbaric Oxygen Therapy in Ulcerative Colitis Patients.

BACKGROUND & AIMS: Hyperbaric oxygen therapy (HBOT) is a promising treatment for moderate-to-severe ulcerative colitis. However, our current understanding of the host and microbial response to HBOT remains unclear. This study examined the molecular mechanisms underpinning HBOT using a multi-omic strategy. METHODS: Pre- and post-intervention mucosal biopsies, tissue, and fecal samples were collected from HBOT phase 2 clinical trials. Biopsies and fecal samples were subjected to shotgun metaproteomics, metabolomics, 16s rRNA sequencing, and metagenomics. Tissue was subjected to bulk RNA sequencing and digital spatial profiling (DSP) for single-cell RNA and protein analysis, and immunohistochemistry was performed. Fecal samples were also used for colonization experiments in IL10-/- germ-free UC mouse models. RESULTS: Proteomics identified negative associations between HBOT response and neutrophil azurophilic granule abundance. DSP identified an HBOT-specific reduction of neutrophil STAT3, which was confirmed by immunohistochemistry. HBOT decreased microbial diversity with a proportional increase in Firmicutes and a secondary bile acid lithocholic acid. A major source of the reduction in diversity was the loss of mucus-adherent taxa, resulting in increased MUC2 levels post-HBOT. Targeted database searching revealed strain-level associations between Akkermansia muciniphila and HBOT response status. Colonization of IL10-/- with stool obtained from HBOT responders resulted in lower colitis activity compared with non-responders, with no differences in STAT3 expression, suggesting complementary but independent host and microbial responses. CONCLUSIONS: HBOT reduces host neutrophil STAT3 and azurophilic granule activity in UC patients and changes in microbial composition and metabolism in ways that improve colitis activity. Intestinal microbiota, especially strain level variations in A muciniphila, may contribute to HBOT non-response.

Tracheostomy in the COVID19 Patients: Our Experience in 12 Cases.

The incidence of tracheostomy has been significantly increased with the increase of patients admitted to the intensive care units. Looking into the literature, there have been various protocols proposed in the past for tracheostomy in COVID 19 patients. In the present case series, we have presented our experience of surgical tracheostomy in COVID 19 patients. It is a retrospective case series consisting of 12 COVID 19 patients who underwent tracheostomy from April 2020 to October 2020. We have discussed the tracheostomy in COVID 19 patients with references to their respective indication, location, the procedure, postoperative care and clinical outcomes. Of 12 patients, 6 were operated in the COVID ICU and 6 were operated in the COVID OT. The average duration of the intubation was 4 days (range 3-7 days). The average period of weaning was found to be 65 h (range 48 h 80 h). Of 4 patients associated with comorbidities, two had died 48 h after the surgery. The Primary indication of the tracheostomy can be made flexible based on the infrastructure of the hospital to accommodate increased patient load in a developing country like India. The location and surgical approach does not significantly affect the clinical outcomes of tracheostomy, and it can be safely performed in ICU/OT with adequate ventilation. Irrespective of the COVID status of the patients, Personal Protective Equipment (PPE) can ensure adequate protection to the health care personals preventing the spread of infection.

Predisposing factors of rhino-orbital-cerebral mucormycosis in patients with COVID 19 infection.

The predisposing factors of invasive fungal disease in COVID 19 infection are still debatable because of the limited human understanding of the virus with the current literature. In this study, we have tried to correlate the various predisposing factors influencing the clinical profile and treatment outcomes in patients with covid associated mucormycosis (CAM). It is a retrospective analysis of cases of CAM during the second wave of COVID 19 infection, which was managed in the department of Otorhinolaryngology from Dec 1, 2020, to June 10, 2021. The detailed clinical, radiological and management of patients with CAM were collected, recorded, evaluated and correlated with the predisposing factors. Of the total, 46 patients, 44(95.65%) were diabetic and 41 patients had a previous history of steroid intake. When clinical parameters were compared between blood sugar < 200 mg/dl and > 200 mg/dl, the old and newly diagnosed diabetes mellitus in patients with CAM, there was no significant differences in any of the above clinical parameters (p > 0.05), except the hospital stay (p = 0,004). Steroid intake in patients with coexisting DM associated with CAM is considered the most important factor for the development of the CAM. There was are no significant difference in any of the clinical/treatment outcomes in patients with CAM with respect to the initial blood sugar, except for the hospital stay. A large sample size with a long-term follow-up period may be needed for a better understanding of common predisposing factors for the development of CAM.

Artificial intelligence guided discovery of a barrier-protective therapy in inflammatory bowel disease.

Modeling human diseases as networks simplify complex multi-cellular processes, helps understand patterns in noisy data that humans cannot find, and thereby improves precision in prediction. Using Inflammatory Bowel Disease (IBD) as an example, here we outline an unbiased AI-assisted approach for target identification and validation. A network was built in which clusters of genes are connected by directed edges that highlight asymmetric Boolean relationships. Using machine-learning, a path of continuum states was pinpointed, which most effectively predicted disease outcome. This path was enriched in gene-clusters that maintain the integrity of the gut epithelial barrier. We exploit this insight to prioritize one target, choose appropriate pre-clinical murine models for target validation and design patient-derived organoid models. Potential for treatment efficacy is confirmed in patient-derived organoids using multivariate analyses. This AI-assisted approach identifies a first-in-class gut barrier-protective agent in IBD and predicted Phase-III success of candidate agents.

COVID Key: A Multifunctional Device to Avoid Touch.

COVID-19 is a global pandemic caused by the novel coronavirus. Although the surfaces pose a low risk of transmission, it is beneficial to use a handheld key-like device to avoid touching the surfaces, especially in public places. The present article reveals a novel design for a multifunctional handheld device, termed the COVID key. The proposed COVID key exhibits ten distinct features, viz. doorknob opener, pushing, pulling, forceps action, sharp edge, key chain, smartphone stand, and a linear and angular scale frequently used in daily life. Theoretical and computational analyses are carried out to check the validity of the design under different loading conditions resembling everyday use. Topological optimization is carried out to achieve the best stiffness-to-weight ratio. The final design is 3D printed in two different materials, ABS (acrylonitrile-butadiene-styrene) and PLA (poly-lactic-acid), using fused deposition based additive manufacturing. Testing and validation of the design are carried out with everyday actions. The COVID keys are distributed among a group of ten unbiased users. The user satisfaction score is recorded based on six basic metrics, viz. ease of use, size, strength, appearance, material and ease of carrying. A satisfaction score of 85% is reported, with ABS being the preferred material of choice.

The stress polarity signaling (SPS) pathway serves as a marker and a target in the leaky gut barrier: implications in aging and cancer.

The gut barrier separates trillions of microbes from the largest immune system in the body; when compromised, a "leaky" gut barrier fuels systemic inflammation, which hastens the progression of chronic diseases. Strategies to detect and repair the leaky gut barrier remain urgent and unmet needs. Recently, a stress-polarity signaling (SPS) pathway has been described in which the metabolic sensor, AMP-kinase acts via its effector, GIV (also known as Girdin) to augment epithelial polarity exclusively under energetic stress and suppresses tumor formation. Using murine and human colon-derived organoids, and enteroid-derived monolayers (EDMs) that are exposed to stressors, we reveal that the SPS-pathway is active in the intestinal epithelium and requires a catalytically active AMP-kinase. Its pharmacologic augmentation resists stress-induced collapse of the epithelium when challenged with microbes or microbial products. In addition, the SPS-pathway is suppressed in the aging gut, and its reactivation in enteroid-derived monolayers reverses aging-associated inflammation and loss of barrier function. It is also silenced during progression of colorectal cancers. These findings reveal the importance of the SPS-pathway in the gut and highlights its therapeutic potential for treating gut barrier dysfunction in aging, cancer, and dysbiosis.

Host engulfment pathway controls inflammation in inflammatory bowel disease.

Chronic diseases, including inflammatory bowel disease (IBD) urgently need new biomarkers as a significant proportion of patients, do not respond to current medications. Inflammation is a common factor in these diseases, and microbial sensing in the intestinal tract is critical to initiate the inflammation. We have identified ELMO1 (engulfment and cell motility protein 1) as a microbial sensor in epithelial and phagocytic cells that turns on inflammatory signals. Using a stem cell-based 'gut-in-a-dish' coculture model, we studied the interactions between microbes, epithelium, and monocytes in the context of IBD. To mimic the in vivo cell physiology, enteroid-derived monolayers (EDMs) were generated from the organoids isolated from WT and ELMO1-/- mice and colonic biopsies of IBD patients. The EDMs were infected with the IBD-associated microbes to monitor the inflammatory responses. ELMO1-depleted EDMs displayed a significant reduction in bacterial internalization, a decrease in pro-inflammatory cytokine productions and monocyte recruitment. The expression of ELMO1 is elevated in the colonic epithelium and in the inflammatory infiltrates within the lamina propria of IBD patients where the higher expression is positively correlated with the elevated expression of pro-inflammatory cytokines, MCP-1 and TNF-α. MCP-1 is released from the epithelium and recruits monocytes to the site of inflammation. Once recruited, monocytes require ELMO1 to engulf the bacteria and propagate a robust TNF-α storm. These findings highlight that the dysregulated epithelial ELMO1 â†’ MCP-1 axis can serve as an early biomarker in the diagnostics of IBD and other inflammatory disorders.

Two Isoforms of the Guanine Nucleotide Exchange Factor, Daple/CCDC88C Cooperate as Tumor Suppressors.

Previously, Aznar et al., showed that Daple/CCDC88C enables Wnt receptors to transactivate trimeric G-proteins during non-canonical Wnt signaling via a novel G-protein binding and activating (GBA) motif. By doing so, Daple serves two opposing roles; earlier during oncogenesis it suppresses neoplastic transformation and tumor growth, but later it triggers epithelial-to-mesenchymal-transition (EMT). We have identified and characterized two isoforms of the human Daple gene. While both isoforms cooperatively suppress tumor growth via their GBA motif, only the full-length transcript triggers EMT and invasion. Both isoforms are suppressed during colon cancer progression, and their reduced expression carries additive prognostic significance. These findings provide insights into the opposing roles of Daple during cancer progression and define the G-protein regulatory GBA motif as one of the minimal modules essential for Daple's role as a tumor suppressor.

Decreasing the Time to Administration of First Dose of Antibiotics in Children With Severe Sepsis.

OBJECTIVES: To measure difference in median time to antibiotic administration in severe sepsis before and after making process changes and clinical outcomes such as duration of hospitalization and mortality. METHODS: The study was carried out in the emergency department in children <17 years of age with severe sepsis/septic shock. In phase 1, data were collected and reasons for delayed antibiotic administration were identified. Following this, process changes like creating a triage tool, re-enforcing the severe sepsis protocol and increasing the number of nurses were made to correct the delay. In phase 2, we measured outcomes to compare the effect of the process changes. RESULTS: A total of 28 and 13 children each were included during phase 1 and phase 2 of the study respectively. The median interquartile range time to administration of antibiotics from the time of admission decreased significantly from 50 minutes (18, 65) to 20 minutes (15, 20) (p = .02). Duration of hospital stay was longer in phase 1 as compared to phase 2 (12 days vs. 6 days). However, the difference was not statistically significant (p = .1). CONCLUSIONS: Use of a triage tool, severe sepsis protocol, and increasing the number of nurses resulted in earlier recognition and administration of first dose of antibiotics in children with severe sepsis.

Drug Authorization for Sofosbuvir/Ledipasvir (Harvoni) for Chronic HCV Infection in a Real-World Cohort: A New Barrier in the HCV Care Cascade.

BACKGROUND: New treatments for hepatitis C (HCV) infection hold great promise for cure, but numerous challenges to diagnosing, establishing care, and receiving therapy exist. There are limited data on insurance authorization for these medications. MATERIALS AND METHODS: We performed a retrospective chart review of patients receiving sofosbuvir/ledipasvir (SOF/LED) from October 11-December 31, 2014 to determine rates and timing of drug authorization. We also determined predictors of approval, and those factors associated with faster decision and approval times. RESULTS: Of 174 patients prescribed HCV therapy during this period, 129 requests were made for SOF/LED, of whom 100 (77.5%) received initial approval, and an additional 17 patients (13.9%) ultimately received approval through the appeals process. Faster approval times were seen in patients with Child-Pugh Class B disease (14.4 vs. 24.7 days, p = 0.048). A higher proportion of patients were initially approved in those with Medicare/Medicaid coverage (92.2% vs. 71.4%, p = 0.002) and those with baseline viral load ≥ 6 million IU/mL (84.1% vs. 62.5%, p = 0.040). Linear regression modeling identified advanced fibrosis, high Model of End Stage Liver Disease (MELD) score, and female gender as significant predictors of shorter decision and approval times. On logistic regression, Medicare/Medicaid coverage (OR 5.96, 95% CI 1.66-21.48) and high viral load (OR 4.52, 95% CI 1.08-19.08) were significant predictors for initial approval. CONCLUSIONS: Early analysis of real-world drug authorization outcomes between October-December 2014 reveals that nearly one in four patients are initially denied access to SOF/LED upon initial prescription, although most patients are eventually approved through appeal, which delays treatment initiation. Having Medicare/Medicaid and advanced liver disease resulted in a higher likelihood of approval as well as earlier decision and approval times. More studies are needed to determine factors resulting in higher likelihood of denial and to evaluate approval rates and times after implementation of restrictive prior authorization guidelines.

GIV/Girdin is a central hub for profibrogenic signalling networks during liver fibrosis.

Progressive liver fibrosis is characterized by the deposition of collagen by activated hepatic stellate cells (HSCs). Activation of HSCs is a multiple receptor-driven process in which profibrotic signals are enhanced and antifibrotic pathways are suppressed. Here we report the discovery of a signalling platform comprising G protein subunit, Gαi and GIV, its guanine exchange factor (GEF), which serves as a central hub within the fibrogenic signalling network initiated by diverse classes of receptors. GIV is expressed in the liver after fibrogenic injury and is required for HSC activation. Once expressed, GIV enhances the profibrotic (PI3K-Akt-FoxO1 and TGFß-SMAD) and inhibits the antifibrotic (cAMP-PKA-pCREB) pathways to skew the signalling network in favour of fibrosis, all via activation of Gαi. We also provide evidence that GIV may serve as a biomarker for progression of fibrosis after liver injury and a therapeutic target for arresting and/or reversing HSC activation during liver fibrosis.

Protein kinase C-theta (PKCθ) phosphorylates and inhibits the guanine exchange factor, GIV/Girdin.

Gα-interacting, vesicle-associated protein (GIV/Girdin) is a multidomain signal transducer that enhances PI3K-Akt signals downstream of both G-protein-coupled receptors and growth factor receptor tyrosine kinases during diverse biological processes and cancer metastasis. Mechanistically, GIV serves as a non-receptor guanine nucleotide exchange factor (GEF) that enhances PI3K signals by activating trimeric G proteins, Gαi1/2/3. Site-directed mutations in GIV's GEF motif disrupt its ability to bind or activate Gi and abrogate PI3K-Akt signals; however, nothing is known about how GIV's GEF function is regulated. Here we report that PKCθ, a novel protein kinase C, down-regulates GIV's GEF function by phosphorylating Ser(S)1689 located within GIV's GEF motif. We demonstrate that PKCθ specifically binds and phosphorylates GIV at S1689, and this phosphoevent abolishes GIV's ability to bind and activate Gαi. HeLa cells stably expressing the phosphomimetic mutant of GIV, GIV-S1689→D, are phenotypically identical to those expressing the GEF-deficient F1685A mutant: Actin stress fibers are decreased and cell migration is inhibited whereas cell proliferation is triggered, and Akt (a.k.a. protein kinase B, PKB) activation is impaired downstream of both the lysophosphatidic acid receptor, a G-protein-coupled receptor, and the insulin receptor, a receptor tyrosine kinase. These findings indicate that phosphorylation of GIV by PKCθ inhibits GIV's GEF function and generates a unique negative feedback loop for downregulating the GIV-Gi axis of prometastatic signaling downstream of multiple ligand-activated receptors. This phosphoevent constitutes the only regulatory pathway described for terminating signaling by any of the growing family of nonreceptor GEFs that modulate G-protein activity.

STAT3 protein up-regulates Gα-interacting vesicle-associated protein (GIV)/Girdin expression, and GIV enhances STAT3 activation in a positive feedback loop during wound healing and tumor invasion/metastasis.

Gα-interacting vesicle-associated protein (GIV) is a guanine nucleotide exchange factor that modulates key signaling pathways during a diverse set of biological processes, e.g. wound healing, macrophage chemotaxis, tumor angiogenesis, vascular repair, and cancer invasion/metastasis. We recently demonstrated that GIV is a metastasis-related protein, which serves both as a therapeutic target and as a biomarker for prognostication in cancer patients. Here we report the discovery that GIV is a direct target of the transcription factor signal transducer and activator of transcription-3 (STAT3), which is commonly known as a central regulator of tumor metastasis. We identified a single STAT3-binding site on the GIV promoter that was necessary and sufficient for transcriptional activation of GIV during wound healing and cancer invasion. Immunohistochemical analysis of breast carcinomas showed significant correlation between STAT3 activation and elevated GIV expression. Furthermore, we provide evidence that GIV positively autoregulates its own transcription by enhancing STAT3 activation via its guanine nucleotide exchange factor activity. Our findings provide mechanistic insights into how STAT3 activation is directly integrated with the receptor tyrosine kinase-GIV-G protein signaling axis. The forward feedback regulation we describe here between GIV and STAT3 may have profound therapeutic implications for cancer and epithelial regeneration/repair and could help invent novel approaches in treating and prognosticating cancer.

Tyrosine phosphorylation of the Gα-interacting protein GIV promotes activation of phosphoinositide 3-kinase during cell migration.

GIV (Gα-interacting vesicle-associated protein; also known as Girdin) enhances Akt activation downstream of multiple growth factor- and G protein (heterotrimeric guanosine 5'-triphosphate-binding protein)-coupled receptors to trigger cell migration and cancer invasion. We demonstrate that GIV is a tyrosine phosphoprotein that directly binds to and activates phosphoinositide 3-kinase (PI3K). Upon ligand stimulation of various receptors, GIV was phosphorylated at tyrosine-1764 and tyrosine-1798 by both receptor and non-receptor tyrosine kinases. These phosphorylation events enabled direct binding of GIV to the amino- and carboxyl-terminal Src homology 2 domains of p85α, a regulatory subunit of PI3K; stabilized receptor association with PI3K; and enhanced PI3K activity at the plasma membrane to trigger cell migration. Tyrosine phosphorylation of GIV and its association with p85α increased during metastatic progression of a breast carcinoma. These results suggest a mechanism by which multiple receptors activate PI3K through tyrosine phosphorylation of GIV, thereby making the GIV-PI3K interaction a potential therapeutic target within the PI3K-Akt pathway.

Src homology domain 2-containing protein-tyrosine phosphatase-1 (SHP-1) binds and dephosphorylates G(alpha)-interacting, vesicle-associated protein (GIV)/Girdin and attenuates the GIV-phosphatidylinositol 3-kinase (PI3K)-Akt signaling pathway.

GIV (Gα-interacting vesicle-associated protein, also known as Girdin) is a bona fide enhancer of PI3K-Akt signals during a diverse set of biological processes, e.g. wound healing, macrophage chemotaxis, tumor angiogenesis, and cancer invasion/metastasis. We recently demonstrated that tyrosine phosphorylation of GIV by receptor and non-receptor-tyrosine kinases is a key step that is required for GIV to directly bind and enhance PI3K activity. Here we report the discovery that Src homology 2-containing phosphatase-1 (SHP-1) is the major protein-tyrosine phosphatase that targets two critical phosphotyrosines within GIV and antagonizes phospho-GIV-dependent PI3K enhancement in mammalian cells. Using phosphorylation-dephosphorylation assays, we demonstrate that SHP-1 is the major and specific protein-tyrosine phosphatase that catalyzes the dephosphorylation of tyrosine-phosphorylated GIV in vitro and inhibits ligand-dependent tyrosine phosphorylation of GIV downstream of both growth factor receptors and GPCRs in cells. In vitro binding and co-immunoprecipitation assays demonstrate that SHP-1 and GIV interact directly and constitutively and that this interaction occurs between the SH2 domain of SHP-1 and the C terminus of GIV. Overexpression of SHP-1 inhibits tyrosine phosphorylation of GIV and formation of phospho-GIV-PI3K complexes, and specifically suppresses GIV-dependent activation of Akt. Consistently, depletion of SHP-1 enhances peak tyrosine phosphorylation of GIV, which coincides with an increase in peak Akt activity. We conclude that SHP-1 antagonizes the action of receptor and non-receptor-tyrosine kinases on GIV and down-regulates the phospho-GIV-PI3K-Akt axis of signaling.