Vol. 276, Issue 2, C487-C496, February 1999
Adenylyl cyclase P-site ligands accelerate differentiation in
Ob1771 preadipocytes
Azeddine
Ibrahimi,
Nada
Abumrad,
Hengameh
Maghareie,
Michael
Golia,
Ilana
Shoshani,
Laurent
Désaubry, and
Roger A.
Johnson
Department of Physiology and Biophysics, State University of New
York, Stony Brook, New York 11794-8661
Differentiation of Ob1771 preadipocytes to adipocytes was
characterized by morphological changes and elevated expression of the
specific marker enzyme, glycerol-3-phosphate dehydrogenase. A
differentiation response substantially more complete and rapid than
that obtained with insulin and 3,5,3'-triiodothyronine was observed with established inhibitors of adenylyl cyclases:
2',5'-dideoxyadenosine (2',5'-dd-Ado),
9-(cyclopentyl)adenine (9-CP-Ade), and 9-(arabinofuranosyl)adenine (9-Ara-Ade), coincident with decreased cellular cAMP levels. These ligands inhibit adenylyl cyclases noncompetitively, via a domain referred to as the P-site because of its requirement for an intact purine moiety. Differentiation was not induced by inosine, a nucleoside known not to act at the P-site, or by
N6-(2-phenylisopropyl)adenosine
or 1,3-diethyl-8-phenylxanthine, agonist and antagonist, respectively,
for adenosine A1 receptors. Also
ineffective were IBMX or forskolin, agents that can raise intracellular
cAMP levels. Potency of the differentiation response followed the order
2',5'-dd-Ado (1-20 µM) > 9-CP-Ade (10-100
µM) = 9-Ara-Ade (10-100 µM) >> inosine, consistent with
their potencies to inhibit adenylyl cyclases. The data suggest that
inhibition of adenylyl cyclase via the P-site and the consequent
reduction in cell cAMP levels facilitate the induction of
differentiation in Ob1771 cells. The findings raise the question
whether the known endogenous P-site ligands participate in the
differentiation response induced by hormones.
adipocytes; P-site inhibition; 2',5'-dideoxyadenosine; 9-(cyclopentyl)adenine; signal transduction; adenosine
3',5'-cyclic monophosphate
