ACCELERATED PUBLICATION
Pertussis Toxin-insensitive Activation of the Heterotrimeric
G-proteins Gi/Go by the NG108-15 G-protein
Activator*
Catalina
Ribas
§,
Aya
Takesono¶,
Motohiko
Sato
,
John D.
Hildebrandt**, and
Stephen M.
Lanier
From the Centro de Biología Molecular,
"Severo Ochoa" (CSIC-UAM), Universidad Autonoma de Madrid,
Cantoblanco, 28049-Madrid, Spain, the ** Department of
Pharmacology, Medical University of South Carolina, Charleston, South
Carolina 29425, the Department of Pharmacology and
Experimental Therapeutics, Louisiana State University Health Sciences
Center, New Orleans, Louisiana 70112, and the ¶ National Human
Genome Research Institute, Bethesda, Maryland 20892
A ligand-independent activator of
heterotrimeric brain G-protein was partially purified from
detergent-solubilized extracts of the neuroblastoma-glioma cell hybrid
NG108-15. The G-protein activator (NG108-15 G-protein activator
(NG-GPA)) increased [35S]guanosine
5'-O-(thiotriphosphate) ([35S]GTP
S) to
purified brain G-protein in a magnesium-dependent manner
and promoted GDP dissociation from G
o. The NG-GPA
also increased GTPS binding to purified, recombinant
Gi2, Gi3, and Go, but
minimally altered nucleotide binding to purified transducin. The NG-GPA
increased GTPS binding to membrane-bound G-proteins and inhibited
basal, forskolin- and hormone-stimulated adenylyl cyclase activity in
DDT1-MF-2 cell membranes. In contrast to G-protein coupled
receptor-mediated activation of heterotrimeric G-proteins in
DDT1-MF-2 cell membrane preparations, the action of the
NG-GPA was not altered by treatment of the cells with pertussis toxin. ADP-ribosylation of purified brain G-protein also failed to alter the
increase in GTPS binding elicited by the NG-GPA. Thus, the NG-GPA
acts in a manner distinct from that of a G-protein coupled receptor and
other recently described receptor-independent activators of G-protein
signaling. These data indicate the presence of unexpected regulatory
domains on Gi/Go proteins and suggest the
existence of pertussis toxin-insensitive modes of signal input to
Gi/Go signaling systems.
*
This work was supported by the National Institutes of Health
Grants RO1-NS24821 and MH59931 (to S. M. L.) and DK37219 (to J. D. H.).The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement" in
accordance with 18 U.S.C. Section
1734 solely to indicate this fact.
§
Recipient of a Medical University of South Carolina Health Sciences
Foundation Research Fellowship, a Ministerio de Educación y
Ciencia Postdoctoral Fellowship (Spain), and the Programa Ramón y
Cajal (Ministerio de Ciencia y Tecnología).
To whom correspondence should be addressed: Dept. of
Pharmacology and Experimental Therapeutics, Louisiana State University Health Sciences Center, 1901 Perdido St., New Orleans, LA 70112. Tel.:
504-568-4740; Fax: 504-568-2361; E-mail:
slanie@lsuhsc.edu.
Copyright © 2002 by The American Society for Biochemistry and Molecular Biology, Inc.
