The tumor suppressor folliculin inhibits lactate dehydrogenase A and regulates the Warburg effect.

Aerobic glycolysis in cancer cells, also known as the 'Warburg effect', is driven by hyperactivity of lactate dehydrogenase A (LDHA). LDHA is thought to be a substrate-regulated enzyme, but it is unclear whether a dedicated intracellular protein also regulates its activity. Here, we identify the human tumor suppressor folliculin (FLCN) as a binding partner and uncompetitive inhibitor of LDHA. A flexible loop within the amino terminus of FLCN controls movement of the LDHA active-site loop, tightly regulating its enzyme activity and, consequently, metabolic homeostasis in normal cells. Cancer cells that experience the Warburg effect show FLCN dissociation from LDHA. Treatment of these cells with a decapeptide derived from the FLCN loop region causes cell death. Our data suggest that the glycolytic shift of cancer cells is the result of FLCN inactivation or dissociation from LDHA. Together, FLCN-mediated inhibition of LDHA provides a new paradigm for the regulation of glycolysis.

MMPs, tyrosine kinase signaling and extracellular matrix proteolysis in kidney cancer.

Patients diagnosed with metastatic renal cell carcinoma (RCC) have ∼12% chance for 5-year survival. The integrity of the extracellular matrix (ECM) that surrounds tumor cells influences their behavior and, when disturbed, it could facilitate local invasion and spread of tumor cells to distant sites. The interplay between von Hippel-Lindau/hypoxia inducible factor signaling axis and activated kinase networks results in aberrant ECM and tumor progression. Matrix metalloproteinases (MMPs) are proteolytic enzymes implicated in ECM remodeling, tumor angiogenesis, and immune cell infiltration. Understanding the cross-talk between kinase signaling and ECM proteolysis in RCC could provide insights into developing drugs that interfere specifically with the process of invasion. In this review, we discuss changes in the MMPs/ECM axis in RCC, prominent kinase signaling pathways implicated in MMPs induction, and comment on emerging extracellular regulatory networks that modulate MMPs activity.

Co-chaperones TIMP2 and AHA1 Competitively Regulate Extracellular HSP90:Client MMP2 Activity and Matrix Proteolysis.

The extracellular molecular chaperone heat shock protein 90 (eHSP90) stabilizes protease client the matrix metalloproteinase 2 (MMP2), leading to tumor cell invasion. Although co-chaperones are critical modulators of intracellular HSP90:client function, how the eHSP90:MMP2 complex is regulated remains speculative. Here, we report that the tissue inhibitor of metalloproteinases-2 (TIMP2) is a stress-inducible extracellular co-chaperone that binds to eHSP90, increases eHSP90 binding to ATP, and inhibits its ATPase activity. In addition to disrupting the eHSP90:MMP2 complex and terminally inactivating MMP2, TIMP2 loads the client to eHSP90, keeping the protease in a transient inhibitory state. Secreted activating co-chaperone AHA1 displaces TIMP2 from the complex, providing a "reactivating" mechanism for MMP2. Gene knockout or blocking antibodies targeting TIMP2 and AHA1 released by HT1080 cancer cells modify their gelatinolytic activity. Our data suggest that TIMP2 and AHA1 co-chaperones function as a molecular switch that determines the inhibition and reactivation of the eHSP90 client protein MMP2.

Regulation of transient receptor potential cation channel subfamily V1 protein synthesis by the phosphoinositide 3-kinase/Akt pathway in colonic hypersensitivity.

The transient receptor potential cation channel subfamily V member 1 (TRPV1), also known as the capsaicin receptor or vanilloid receptor 1 (VR1), is expressed in nociceptive neurons in the dorsal root ganglia (DRG) and participates in the transmission of pain. The present study investigated the underlying molecular mechanisms by which TRPV1 was regulated by nerve growth factor (NGF) signaling pathways in colonic hypersensitivity in response to colitis. We found that during colitis TRPV1 protein levels were significantly increased in specifically labeled colonic afferent neurons in both L1 and S1 DRGs. TRPV1 protein up-regulation in DRG was also enhanced by NGF treatment. We then found that TRPV1 protein up-regulation in DRG was regulated by activation of the phosphoinositide 3-kinase (PI3K)/Akt pathway both in vivo and in vitro. Suppression of endogenous PI3K/Akt activity during colitis or NGF treatment with a specific PI3K inhibitor LY294002 reduced TRPV1 protein production in DRG neurons, and also reduced colitis-evoked TRPV1-mediated visceral hypersensitivity tested by hyper-responsiveness to colorectal distention (CRD) and von Frey filament stimulation of abdomen. Further studies showed that TRPV1 mRNA levels in the DRG were not regulated by either colitis or NGF. We then found that an up-regulation of the protein synthesis pathway was involved by which both colitis and NGF caused a PI3K-dependent increase in the phosphorylation level of eukaryotic translation initiation factor 4E-binding protein (4E-BP)1. These results suggest a novel mechanism in colonic hypersensitivity which involves PI3K/Akt-mediated TRPV1 protein, not mRNA, up-regulation in primary afferent neurons, likely through activation of the protein synthesis pathways.

EXPRESS: Phospholipase C gamma mediates endogenous brain-derived neurotrophic factor - regulated calcitonin gene-related peptide expression in colitis - induced visceral pain.

BACKGROUND: Visceral hypersensitivity is a complex pathophysiological paradigm with unclear mechanisms. Primary afferent neuronal plasticity marked by alterations in neuroactive compounds such as calcitonin gene-related peptide is suggested to underlie the heightened sensory responses. Signal transduction that leads to calcitonin gene-related peptide expression thereby sensory neuroplasticity during colitis remains to be elucidated. RESULTS: In a rat model with colitis induced by 2,4,6-trinitrobenzene sulfonic acid, we found that endogenously elevated brain-derived neurotrophic factor elicited an up-regulation of calcitonin gene-related peptide in the lumbar L1 dorsal root ganglia. At seven days of colitis, neutralization of brain-derived neurotrophic factor with a specific brain-derived neurotrophic factor antibody reversed calcitonin gene-related peptide up-regulation in the dorsal root ganglia. Colitis-induced calcitonin gene-related peptide transcription was also inhibited by brain-derived neurotrophic factor antibody treatment. Signal transduction studies with dorsal root ganglia explants showed that brain-derived neurotrophic factor-induced calcitonin generelated peptide expression was mediated by the phospholipase C gamma, but not the phosphatidylinositol 3-kinase/Akt or the mitogen-activated protein kinase/extracellular signal-regulated protein kinase pathway. Application of PLC inhibitor U73122 in vivo confirmed that colitis-induced and brain-derived neurotrophic factor-mediated calcitonin gene-related peptide up-regulation in the dorsal root ganglia was regulated by the phospholipase C gamma pathway. In contrast, suppression of the phosphatidylinositol 3-kinase activity in vivo had no effect on colitis-induced calcitonin gene-related peptide expression. During colitis, calcitonin gene-related peptide also co-expressed with phospholipase C gamma but not with p-Akt. Calcitonin gene-related peptide up-regulation during colitis correlated to the activation of cAMP-responsive element binding protein in the same neurons. Consistently, colitis-induced cAMP-responsive element binding protein activation in the dorsal root ganglia was attenuated by brain-derived neurotrophic factor antibody treatment. CONCLUSION: These results suggest that colitis-induced and brain-derived neurotrophic factor-mediated calcitonin generelated peptide expression in sensory activation is regulated by a unique pathway involving brain-derived neurotrophic factorphospholipase C gamma-cAMP-responsive element binding protein axis.

Colitis-induced bladder afferent neuronal activation is regulated by BDNF through PLCγ pathway.

Patients with inflammatory bowel disease (IBD) or irritable bowel syndrome (IBS) often experience increased sensory responsiveness in the urinary bladder reflecting neurogenic bladder overactivity. Here we demonstrate that colitis-induced up-regulation of the phospholipase C gamma (PLCγ) pathway downstream of brain-derived neurotrophic factor (BDNF) in bladder afferent neurons in the dorsal root ganglia (DRG) plays essential roles in activating these neurons thereby leading to bladder hyperactivity. Upon induction of colitis with 2,4,6-trinitrobenzenesulfonic acid (TNBS) in rats, we found that the phosphorylation (activation) level of cAMP responsive element-binding (p-CREB) protein, a molecular switch of neuronal plasticity, was increased in specifically labeled bladder afferent neurons in the thoracolumbar and lumbosacral DRGs. In rats having reduced levels of BDNF (BDNF+/-), colitis failed to elevate CREB protein activity in bladder afferent neurons. Physiological examination also demonstrated that colitis-induced urinary frequency was not shown in BDNF+/- rats, implicating an essential role of BDNF in mediating colon-to-bladder sensory cross-sensitization. We further implemented in vivo and in vitro studies and demonstrated that BDNF-mediated colon-to-bladder sensory cross-activation involved the TrkB-PLCγ-calcium/calmodulin-dependent protein kinase II (CaMKII) cascade. In contrast, the PI3K/Akt pathway was not activated in bladder afferent neurons during colitis and was not involved in BDNF action in the DRG. Our results suggest that colon-to-bladder sensory cross-sensitization is regulated by specific signal transduction initiated by the up-regulation of BDNF in the DRG.

Impact of V-ets Erythroblastosis Virus E26 Oncogene Homolog 1 Gene Polymorphisms Upon Susceptibility to Autoimmune Diseases: A Meta-Analysis.

V-ets erythroblastosis virus E26 oncogene homolog 1 (ETS1) is recognized as a gene of risk to autoimmune diseases (ADs). Two single nucleotide polymorphisms (SNPs) in ETS1 (rs1128334 G>A and rs10893872 T>C) were considered associated with ADs risk. However, the results remain conflicting.We performed a meta-analysis to evaluate more precise estimations of any relationship. We searched PubMed, OvidSP, and Chinese National Knowledge Infrastructure databases (papers published prior to September 12, 2014) and extracted data from eligible studies. Meta-analysis was performed using the STATA 12.0 software. Random effect model or fixed effect model were chosen according to the study heterogeneities.A total of 11 studies including 7359 cases (9660 controls) for rs1128334 and 8 studies including 5419 cases (7122 controls) for rs10893872 were involved in this meta-analysis. Overall, our results showed that there were significant associations for rs1128334 with AD risk in 5 genetic models, both in pooled analysis and in systemic lupus erythematous (SLE) subgroup, and in 3 genetic models of the uveitis subgroup. Although for rs10893872, the results showed that there were significant associations in allele model both in pooled analysis and in SLE subgroup. As a conclusion, this meta-analysis demonstrated that these 2 SNPs (rs1128334 and rs10893872) in ETS1 were associated with ADs risk.