Coordinate down-regulation of adenylyl cyclase isoforms and the stimulatory G protein (G(s)) in intestinal epithelial cell differentiation.
The intestinal epithelium is dynamic, with proliferation of undifferentiated crypt cells balanced by terminal differentiation and cell death at the colon surface or small intestinal villus tips. Cyclic AMP, induced by agonists such as prostaglandin E(2) and vasoactive intestinal polypeptide, promotes proliferation and ion secretion and suppresses apoptosis in intestinal epithelial cells. Here, we show that cell differentiation in a model intestinal epithelium leads to attenuation of cAMP production in response to G protein-coupled receptor and receptor-independent agonists. Concomitantly, key components of the cAMP cascade, the alpha subunit of the stimulatory G protein, G(s), and adenylyl cyclase (AC) isoforms 3, 4, 6, and 7 are down-regulated. By contrast, AC1, AC2, AC8, and AC9, and the receptors for prostaglandin E(2) and vasoactive intestinal polypeptide, are not expressed or not affected by differentiation. We confirmed key findings in normal murine colon epithelium, in which the major AC isoforms and G(s)alpha are markedly down-regulated in differentiated surface cells. Suppression of AC isoforms and G(s)alpha is functionally important, because their constitutive expression completely reverses differentiation-induced cAMP attenuation. Thus, down-regulation of AC isoforms and G(s)alpha is an integral part of the intestinal epithelial differentiation program, perhaps serving to release cells from cAMP-promoted anti-apoptosis as a prerequisite for cell death upon terminal differentiation.
Department of Medicine, University of California, San Diego, La Jolla, California 92093, USA.
Lillian J
LJ
Choi
Gabriela
G
Jenikova
Elaine
E
Hanson
Martina E
ME
Spehlmann
Nicholas S
NS
Boehling
Shelli L
SL
Kirstein
Richard A
RA
Bundey
Jennifer R
JR
Smith
Paul A
PA
Insel
Lars
L
Eckmann
D000262:Adenylyl Cyclases / Q000096:biosynthesis*; D000818:Animals; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D003106:Colon / Q000201:enzymology*; D015232:Dinoprostone / Q000378:metabolism; D015536:Down-Regulation / Q000502:physiology; D004847:Epithelial Cells / Q000201:enzymology*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D006801:Humans; D007413:Intestinal Mucosa / Q000201:enzymology*; D007527:Isoenzymes / Q000096:biosynthesis
D007527:Isoenzymes; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; D015232:Dinoprostone