Hypoxic induction of AKAP12 variant 2 shifts PKA-mediated protein phosphorylation to enhance migration and metastasis of melanoma cells.
Proceedings of the National Academy of Sciences of the United States of America
2015; 112 (14): 4441-4446
Scaffold proteins are critical hubs within cells that have the ability to modulate upstream signaling molecules and their downstream effectors to fine-tune biological responses. Although they can serve as focal points for association of signaling molecules and downstream pathways that regulate tumorigenesis, little is known about how the tumor microenvironment affects the expression and activity of scaffold proteins. This study demonstrates that hypoxia, a common element of solid tumors harboring low oxygen levels, regulates expression of a specific variant of the scaffold protein AKAP12 (A-kinase anchor protein 12), AKAP12v2, in metastatic melanoma. In turn, through a kinome-wide phosphoproteomic and MS study, we demonstrate that this scaffolding protein regulates a shift in protein kinase A (PKA)-mediated phosphorylation events under hypoxia, causing alterations in tumor cell invasion and migration in vitro, as well as metastasis in an in vivo orthotopic model of melanoma. Mechanistically, the shift in AKAP12-dependent PKA-mediated phosphorylations under hypoxia is due to changes in AKAP12 localization vs. structural differences between its two variants. Importantly, our work defines a mechanism through which a scaffold protein can be regulated by the tumor microenvironment and further explains how a tumor cell can coordinate many critical signaling pathways that are essential for tumor growth through one individual scaffolding protein.
View details for DOI 10.1073/pnas.1418164112
View details for PubMedID 25792458
- Direct regulation of GAS6/AXL signaling by HIF promotes renal metastasis through SRC and MET PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2014; 111 (37): 13373-13378
CTGF is a therapeutic target for metastatic melanoma
2014; 33 (9): 1093-1100
Metastatic melanoma remains a devastating disease with a 5-year survival rate of less than five percent. Despite recent advances in targeted therapies for melanoma, only a small percentage of melanoma patients experience durable remissions. Therefore, it is critical to identify new therapies for the treatment of advanced melanoma. Here, we define connective tissue growth factor (CTGF) as a therapeutic target for metastatic melanoma. Clinically, CTGF expression correlates with tumor progression and is strongly induced by hypoxia through HIF-1 and HIF-2-dependent mechanisms. Genetic inhibition of CTGF in human melanoma cells is sufficient to significantly reduce orthotopic tumor growth, as well as metastatic tumor growth in the lung of severe combined immunodeficient (SCID) mice. Mechanistically, inhibition of CTGF decreased invasion and migration associated with reduced matrix metalloproteinase-9 expression. Most importantly, the anti-CTGF antibody, FG-3019, had a profound inhibitory effect on the progression of established metastatic melanoma. These results offer the first preclinical validation of anti-CTGF therapy for the treatment of advanced melanoma and underscore the importance of tumor hypoxia in melanoma progression.Oncogene advance online publication, 25 February 2013; doi:10.1038/onc.2013.47.
View details for DOI 10.1038/onc.2013.47
View details for Web of Science ID 000331933800003
View details for PubMedID 23435419
Cross-talk between hypoxia and insulin signaling through Phd3 regulates hepatic glucose and lipid metabolism and ameliorates diabetes.
2013; 19 (10): 1325-1330
Signaling initiated by hypoxia and insulin powerfully alters cellular metabolism. The protein stability of hypoxia-inducible factor-1 alpha (Hif-1α) and Hif-2α is regulated by three prolyl hydroxylase domain-containing protein isoforms (Phd1, Phd2 and Phd3). Insulin receptor substrate-2 (Irs2) is a critical mediator of the anabolic effects of insulin, and its decreased expression contributes to the pathophysiology of insulin resistance and diabetes. Although Hif regulates many metabolic pathways, it is unknown whether the Phd proteins regulate glucose and lipid metabolism in the liver. Here, we show that acute deletion of hepatic Phd3, also known as Egln3, improves insulin sensitivity and ameliorates diabetes by specifically stabilizing Hif-2α, which then increases Irs2 transcription and insulin-stimulated Akt activation. Hif-2α and Irs2 are both necessary for the improved insulin sensitivity, as knockdown of either molecule abrogates the beneficial effects of Phd3 knockout on glucose tolerance and insulin-stimulated Akt phosphorylation. Augmenting levels of Hif-2α through various combinations of Phd gene knockouts did not further improve hepatic metabolism and only added toxicity. Thus, isoform-specific inhibition of Phd3 could be exploited to treat type 2 diabetes without the toxicity that could occur with chronic inhibition of multiple Phd isoforms.
View details for DOI 10.1038/nm.3294
View details for PubMedID 24037093
TBC1D16 is a Rab4A GTPase activating protein that regulates receptor recycling and EGF receptor signaling
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2012; 109 (39): 15787-15792
Rab4A is a master regulator of receptor recycling from endocytic compartments to the plasma membrane. The protein TBC1D16 is up-regulated in melanoma, and TBC1D16-overexpressing melanoma cells are dependent on TBC1D16. We show here that TBC1D16 enhances the intrinsic rate of GTP hydrolysis by Rab4A. TBC1D16 is both cytosolic and membrane associated; the membrane-associated pool colocalizes with transferrin and EGF receptors (EGFRs) and early endosome antigen 1, but not with LAMP1 protein. Expression of two TBC1D16 isoforms, but not the inactive R494A mutant, reduces transferrin receptor recycling but has no effect on transferrin receptor internalization. Expression of TBC1D16 alters GFP-Rab4A membrane localization. In HeLa cells, overexpression of TBC1D16 enhances EGF-stimulated EGFR degradation, concomitant with decreased EGFR levels and signaling. Thus, TBC1D16 is a GTPase activating protein for Rab4A that regulates transferrin receptor recycling and EGFR trafficking and signaling.
View details for DOI 10.1073/pnas.1204540109
View details for Web of Science ID 000309604500056
View details for PubMedID 23019362
VHL loss in renal cell carcinoma leads to up-regulation of CUB domain-containing protein 1 to stimulate PKC delta-driven migration
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2011; 108 (5): 1931-1936
A common genetic mutation found in clear cell renal cell carcinoma (CC-RCC) is the loss of the von Hippel-Lindau (VHL) gene, which results in stabilization of hypoxia-inducible factors (HIFs), and contributes to cancer progression and metastasis. CUB-domain-containing protein 1 (CDCP1) was shown to promote metastasis in scirrhous and lung adenocarcinomas as well as in prostate cancer. In this study, we established a molecular mechanism linking VHL loss to induction of the CDCP1 gene through the HIF-1/2 pathway in renal cancer. Also, we report that Fyn, which forms a complex with CDCP1 and mediates its signaling to PKC?, is a HIF-1 target gene. Mechanistically, we found that CDCP1 specifically regulates phosphorylation of PKC?, but not of focal adhesion kinase or Crk-associated substrate. Signal transduction from CDCP1 to PKC? leads to its activation, increasing migration of CC-RCC. Furthermore, patient survival can be stratified by CDCP1 expression at the cell surface of the tumor. Taken together, our data indicates that CDCP1 protein might serve as a therapeutic target for CC-RCC.
View details for DOI 10.1073/pnas.1011777108
View details for Web of Science ID 000286804700036
View details for PubMedID 21233420
Hypoxia, inflammation, and the tumor microenvironment in metastatic disease
CANCER AND METASTASIS REVIEWS
2010; 29 (2): 285-293
Metastasis, the leading cause of cancer deaths, is an intricate process involving many important tumor and stromal proteins that have yet to be fully defined. This review discusses critical components necessary for the metastatic cascade, including hypoxia, inflammation, and the tumor microenvironment. More specifically, this review focuses on tumor cell and stroma interactions, which allow cell detachment from a primary tumor, intravasation to the blood stream, and extravasation at a distant site where cells can seed and tumor metastases can form. Central players involved in this process and discussed in this review include integrins, matrix metalloproteinases, and soluble growth factors/matrix proteins, including the connective tissue growth factor and lysyl oxidase.
View details for DOI 10.1007/s10555-010-9224-5
View details for Web of Science ID 000277411300006
View details for PubMedID 20393783
Endocytosis of the Type III Transforming Growth Factor-beta (TGF-beta) Receptor through the Clathrin-independent/Lipid Raft Pathway Regulates TGF-beta Signaling and Receptor Down-regulation
JOURNAL OF BIOLOGICAL CHEMISTRY
2008; 283 (50): 34808-34818
Transforming growth factor-beta (TGF-beta) signals through three highly conserved cell surface receptors, the type III TGF-beta receptor (T beta RIII), the type II TGF-beta receptor (T beta RII), and the type I TGF-beta receptor (T beta RI) to regulate diverse cellular processes including cell proliferation, differentiation, migration, and apoptosis. Although T beta RI and T beta RII undergo ligand-independent endocytosis by both clathrin-mediated endocytosis, resulting in enhanced signaling, and clathrin-independent endocytosis, resulting in receptor degradation, the mechanism and function of T beta RIII endocytosis is poorly understood. T beta RIII is a heparan sulfate proteoglycan with a short cytoplasmic tail that functions as a TGF-beta superfamily co-receptor, contributing to TGF-beta signaling through mechanisms yet to be fully defined. We have reported previously that T beta RIII endocytosis, mediated by a novel interaction with beta arrestin-2, results in decreased TGF-beta signaling. Here we demonstrate that T beta RIII undergoes endocytosis in a ligand and glycosaminoglycan modification-independent and cytoplasmic domain-dependent manner, with the interaction of Thr-841 in the cytoplasmic domain of T beta RIII with beta-arrestin2 enhancing T beta RIII endocytosis. T beta RIII undergoes both clathrin-mediated and clathrin-independent endocytosis. Importantly, inhibition of the clathrin-independent, lipid raft pathway, but not of the clathrin-dependent pathway, results in decreased TGF-beta1 induced Smad2 and p38 phosphorylation, supporting a specific role for clathrin-independent endocytosis of T beta RIII in regulating both Smad-dependent and Smad-independent TGF-beta signaling.
View details for DOI 10.1074/jbc.M804741200
View details for Web of Science ID 000261469100037
View details for PubMedID 18845534
T beta RIII suppresses non-small cell lung cancer invasiveness and tumorigenicity
2008; 29 (3): 528-535
The transforming growth factor-beta (TGF-beta) superfamily has essential roles in lung development, regulating cell proliferation, branching morphogenesis, differentiation and apoptosis. Although most lung cancers become resistant to the tumor suppressor effects of TGF-beta, and loss or mutation of one of the components of the TGF-beta signaling pathway, including TbetaRII, Smad2 and Smad4 have been reported, mutations are not common in non-small cell lung cancer (NSCLC). Here we demonstrate that the TGF-beta superfamily co-receptor, the type III TGF-beta receptor (TbetaRIII or betaglycan) is lost in the majority of NSCLC specimens at the mRNA and protein levels, with loss correlating with increased tumor grade and disease progression. Loss of heterozygosity at the TGFBR3 genomic locus occurs in 38.5% of NSCLC specimens and correlates with decreased TbetaRIII expression, suggesting loss of heterozygosity as one mechanism for TbetaRIII loss. In the H460 cell model of NSCLC, restoring TbetaRIII expression decreased colony formation in soft agar. In the A549 cell model of NSCLC, restoring TbetaRIII expression significantly decreased cellular migration and invasion through Matrigel, in the presence and absence of TGF-beta1, and decreased tumorigenicity in vivo. In a reciprocal manner, shRNA-mediated silencing of endogenous TbetaRIII expression enhanced invasion through Matrigel. Mechanistically, TbetaRIII functions, at least in part, through undergoing ectodomain shedding, generating soluble TbetaRIII, which is able to inhibit cellular invasiveness. Taken together, these results support TbetaRIII as a novel tumor suppressor gene that is commonly lost in NSCLC resulting in a functional increase in cellular migration, invasion and anchorage-independent growth of lung cancer cells.
View details for DOI 10.1093/carcin/bgm289
View details for Web of Science ID 000254008300009
View details for PubMedID 18174241
The type III transforming growth factor-beta receptor as a novel tumor suppressor gene in prostate cancer
2007; 67 (3): 1090-1098
The transforming growth factor-beta (TGF-beta) signaling pathway has an important role in regulating normal prostate epithelium, inhibiting proliferation, differentiation, and both androgen deprivation-induced and androgen-independent apoptosis. During prostate cancer formation, most prostate cancer cells become resistant to these homeostatic effects of TGF-beta. Although the loss of expression of either the type I (TbetaRI) or type II (TbetaRII) TGF-beta receptor has been documented in approximately 30% of prostate cancers, most prostate cancers become TGF-beta resistant without mutation or deletion of TbetaRI, TbetaRII, or Smads2, 3, and 4, and thus, the mechanism of resistance remains to be defined. Here, we show that type III TGF-beta receptor (TbetaRIII or betaglycan) expression is decreased or lost in the majority of human prostate cancers as compared with benign prostate tissue at both the mRNA and protein level. Loss of TbetaRIII expression correlates with advancing tumor stage and a higher probability of prostate-specific antigen (PSA) recurrence, suggesting a role in prostate cancer progression. The loss of TbetaRIII expression is mediated by the loss of heterozygosity at the TGFBR3 genomic locus and epigenetic regulation of the TbetaRIII promoter. Functionally, restoring TbetaRIII expression in prostate cancer cells potently decreases cell motility and cell invasion through Matrigel in vitro and prostate tumorigenicity in vivo. Taken together, these studies define the loss of TbetaRIII expression as a common event in human prostate cancer and suggest that this loss is important for prostate cancer progression through effects on cell motility, invasiveness, and tumorigenicity.
View details for DOI 10.1158/000805472.CAN-06-3117
View details for Web of Science ID 000244137300033
View details for PubMedID 17283142