Modulation of rap activity by direct interaction of Galpha(o) with Rap1 GTPase-activating protein.

Journal Article (Journal Article)

We used the yeast two-hybrid system to identify proteins that interact directly with Galpha(o). Mutant-activated Galpha(o) was used as the bait to screen a cDNA library from chick dorsal root ganglion neurons. We found that Galpha(o) interacted with several proteins including Gz-GTPase-activating protein (Gz-GAP), a new RGS protein (RGS-17), a novel protein of unknown function (IP6), and Rap1GAP. This study focuses on Rap1GAP, which selectively interacts with Galpha(o) and Galpha(i) but not with Galpha(s) or Galpha(q). Rap1GAP interacts more avidly with the unactivated Galpha(o) as compared with the mutant (Q205L)-activated Galpha(o). When expressed in HEK-293 cells, unactivated Galpha(o) co-immunoprecipitates with the Rap1GAP. Expression of chick Rap1GAP in PC-12 cells inhibited activation of Rap1 by forskolin. When unactivated Galpha(o) was expressed, the amount of activated Rap1 was greatly increased. This effect was not observed with the Q205L-Galpha(o). Expression of unactivated Galpha(o) stimulated MAP-kinase (MAPK1/2) activity in a Rap1GAP-dependent manner. These results identify a novel function of Galpha(o), which in its resting state can sequester Rap1GAP thereby regulating Rap1 activity and consequently gating signal flow from Rap1 to MAPK1/2. Thus, activation of G(o) could modulate the Rap1 effects on a variety of cellular functions.

Full Text

Cited Authors

  • Jordan, JD; Carey, KD; Stork, PJ; Iyengar, R

Published Date

  • July 30, 1999

Published In

Volume / Issue

  • 274 / 31

Start / End Page

  • 21507 - 21510

PubMed ID

  • 10419452

International Standard Serial Number (ISSN)

  • 0021-9258

Digital Object Identifier (DOI)

  • 10.1074/jbc.274.31.21507


  • eng

Conference Location

  • United States