p120Ras-GAP binds the DLC1 Rho-GAP tumor suppressor protein and inhibits its RhoA GTPase and growth-suppressing activities.
DLC1 (deleted in liver cancer 1), which encodes a Rho GTPase-activating protein (Rho-GAP), is a potent tumor suppressor gene that is frequently inactivated in several human cancers. DLC1 is a multidomain protein that has been shown previously to bind members of the tensin gene family. Here we show that p120Ras-GAP (Ras-GAP; also known as RASA1) interacts and extensively colocalizes with DLC1 in focal adhesions. The binding was mapped to the SH3 domain located in the N terminus of Ras-GAP and to the Rho-GAP catalytic domain located in the C terminus of the DLC1. In vitro analyses with purified proteins determined that the isolated Ras-GAP SH3 domain inhibits DLC1 Rho-GAP activity, suggesting that Ras-GAP is a negative regulator of DLC1 Rho-GAP activity. Consistent with this possibility, we found that ectopic overexpression of Ras-GAP in a Ras-GAP-insensitive tumor line impaired the growth-suppressing activity of DLC1 and increased RhoA activity in vivo. Our observations expand the complexity of proteins that regulate DLC1 function and define a novel mechanism of the cross talk between Ras and Rho GTPases.1R01CA129610
Yang
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XY
Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892-4262, USA.
Guan
M
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Vigil
D
D
Der
C J
CJ
Lowy
D R
DR
Popescu
N C
NC
D020134:Catalytic Domain; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D020690:GTPase-Activating Proteins; D006801:Humans; D009369:Neoplasms / Q000473:pathology*; D025521:Tumor Suppressor Proteins / Q000032:analysis / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000502:physiology*; D020729:p120 GTPase Activating Protein / Q000032:analysis / Q000737:chemistry / Q000502:physiology*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*; D018909:src Homology Domains
C112352:DLC1 protein, human; D020690:GTPase-Activating Proteins; D025521:Tumor Suppressor Proteins; D020729:p120 GTPase Activating Protein; C066737:RHOA protein, human; D020742:rhoA GTP-Binding Protein