Functional cross-talk between ras and rho pathways: a Ras-specific GTPase-activating protein (p120RasGAP) competitively inhibits the RhoGAP activity of deleted in liver cancer (DLC) tumor suppressor by masking the catalytic arginine finger.
The three deleted in liver cancer genes (DLC1-3) encode Rho-specific GTPase-activating proteins (RhoGAPs). Their expression is frequently silenced in a variety of cancers. The RhoGAP activity, which is required for full DLC-dependent tumor suppressor activity, can be inhibited by the Src homology 3 (SH3) domain of a Ras-specific GAP (p120RasGAP). Here, we comprehensively investigated the molecular mechanism underlying cross-talk between two distinct regulators of small GTP-binding proteins using structural and biochemical methods. We demonstrate that only the SH3 domain of p120 selectively inhibits the RhoGAP activity of all three DLC isoforms as compared with a large set of other representative SH3 or RhoGAP proteins. Structural and mutational analyses provide new insights into a putative interaction mode of the p120 SH3 domain with the DLC1 RhoGAP domain that is atypical and does not follow the classical PXXP-directed interaction. Hence, p120 associates with the DLC1 RhoGAP domain by targeting the catalytic arginine finger and thus by competitively and very potently inhibiting RhoGAP activity. The novel findings of this study shed light on the molecular mechanisms underlying the DLC inhibitory effects of p120 and suggest a functional cross-talk between Ras and Rho proteins at the level of regulatory proteins.
Institute of Biochemistry and Molecular Biology II, Heinrich Heine University, 40225 Düsseldorf.
Mamta
M
Jaiswal
Institute of Biochemistry and Molecular Biology II, Heinrich Heine University, 40225 Düsseldorf.
Radovan
R
Dvorsky
Institute of Biochemistry and Molecular Biology II, Heinrich Heine University, 40225 Düsseldorf.
Ehsan
E
Amin
Institute of Biochemistry and Molecular Biology II, Heinrich Heine University, 40225 Düsseldorf.
Sarah L
SL
Risse
Institute of Biochemistry and Molecular Biology II, Heinrich Heine University, 40225 Düsseldorf.
Eyad K
EK
Fansa
Institute of Biochemistry and Molecular Biology II, Heinrich Heine University, 40225 Düsseldorf.
Si-Cai
SC
Zhang
Institute of Biochemistry and Molecular Biology II, Heinrich Heine University, 40225 Düsseldorf.
Mohamed S
MS
Taha
Institute of Biochemistry and Molecular Biology II, Heinrich Heine University, 40225 Düsseldorf.
Aziz R
AR
Gauhar
Institute of Biochemistry and Molecular Biology II, Heinrich Heine University, 40225 Düsseldorf.
Saeideh
S
Nakhaei-Rad
Clinic for Gastroenterology, Hepatology and Infectiology, Medical Faculty, Heinrich Heine University, 40225 Düsseldorf.
Claus
C
Kordes
Institute of Biochemistry and Molecular Biology II, Heinrich Heine University, 40225 Düsseldorf.
Katja T
KT
Koessmeier
Institute of Biochemistry and Molecular Biology II, Heinrich Heine University, 40225 Düsseldorf; Leibniz Institute for Age Research, 07745 Jena.
Ion C
IC
Cirstea
Institute of Cell Biology and Immunology, University of Stuttgart, 70569 Stuttgart, Germany.
Monilola A
MA
Olayioye
Clinic for Gastroenterology, Hepatology and Infectiology, Medical Faculty, Heinrich Heine University, 40225 Düsseldorf.
Dieter
D
Häussinger
Institute of Biochemistry and Molecular Biology II, Heinrich Heine University, 40225 Düsseldorf. Electronic address: reza.ahmadian@uni-duesseldorf.de.
Mohammad R
MR
Ahmadian
D000409:Alanine / Q000737:chemistry; D020134:Catalytic Domain; D004252:DNA Mutational Analysis; D020690:GTPase-Activating Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics; D006801:Humans; D053858:Metabolic Networks and Pathways; D011485:Protein Binding; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics; D020729:p120 GTPase Activating Protein / Q000737:chemistry* / Q000235:genetics
C112352:DLC1 protein, human; D020690:GTPase-Activating Proteins; D025521:Tumor Suppressor Proteins; D020729:p120 GTPase Activating Protein; C085379:rho GTPase-activating protein; D000409:Alanine
Arginine Finger; DLC1; Deleted in Liver Cancer; GTPase; Kinetics; Molecular Modeling; RhoGAP; SH3 Domains; Structural Biology; p120RasGAP