טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentBroder Yehoshua
SubjectFunctional Characterization of CHP (CDC42 Homologue
Protein), a Novel Member of the RHO Proteins
DepartmentDepartment of Medicine
Supervisor Professor Ami Aronheim


Abstract

Rho group of small GTPases consists one branch of the Ras superfamily. These GTPases cycle between two states, an active state when bound to GTP and an inactive when bound to GDP. In the active state they interact with downstream molecules (‘effectors’). In addition, Ras and Rho GTPases contain a conserved sequence at their carboxy terminus known as the CAAX motif that is necessary for their targeting to the inner leaflet of the plasma membrane and biological activity.

Cdc42 and Rac1 are the best-characterized members of the Rho group. They control a wide number of biological processes such as reorganization of the actin cytoskeleton, activation of the JNK/SAPK pathways and gene expression, cell cycle progression, embryonic development, axon growth, wound healing, invasion and metastasis.

In this work we present a novel genetic method to identify protein-protein interactions in vivo, designated RRS (Ras Recruitment System). We have used RRS to identify Pak2 (Cdc42 and Rac1 effector) binding partners and we identified a novel small GTPase designated Chp (Cdc42 homologue protein). Chp contains two unique extensions in its amino and carboxy termini, and most strikingly, Chp does not contain the CAAX motif. We examined Chp function in several mammalian cell lines. Here we demonstrate that Chp activities such as, JNK activation, gene expression, cellular localization and interaction with effectors are dependent on its activation state and on the presence of its unique terminal extensions, suggesting a novel mechanism of regulation and function.

This work presents a novel method to identify protein-protein interaction and provides insight into alternative mechanisms of Rho GTPases function in controlling a variety of fundamental biological processes.