Compartmentation of cyclic adenosine 3',5'-monophosphate signaling in caveolae.
The cAMP-signaling pathway is composed of multiple components ranging from receptors, G proteins, and adenylyl cyclase to protein kinase A. A common view of the molecular interaction between them is that these molecules are disseminated on the plasma lipid membrane and random collide with each other to transmit signals. A limitation to this idea, however, is that a signaling cascade involving multiple components may not occur rapidly. Caveolae and their principal component, caveolin, have been implicated in transmembrane signaling, particularly in G protein-coupled signaling. We examined whether caveolin interacts with adenylyl cyclase, the membrane-bound enzyme that catalyzes the conversion of ATP to cAMP. When overexpressed in insect cells, types III, IV, and V adenylyl cyclase were localized in caveolin-enriched membrane fractions. Caveolin was coimmunoprecipitated with adenylyl cyclase in tissue homogenates and copurified with a polyhistidine-tagged form of adenylyl cyclase by Ninitrilotriacetic acid resin chromatography in insect cells, suggesting the colocalization of adenylyl cyclase and caveolin in the same microdomain. Further, the regulatory subunit of protein kinase A (RIIalpha, but not RIalpha) was also enriched in the same fraction as caveolin. Gsalpha was found in both caveolin-enriched and non-caveolin-enriched membrane fractions. Our data suggest that the cAMP-signaling cascade occurs within a restricted microdomain of the plasma membrane in a highly organized manner.
Cardiovascular & Pulmonary Research Institute, Allegheny University of the Health Sciences, Pittsburgh, Pennsylvania 15212, USA.
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C
Schwencke
M
M
Yamamoto
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S
Okumura
Y
Y
Toya
S J
SJ
Kim
Y
Y
Ishikawa
D000262:Adenylyl Cyclases / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism; D000818:Animals; D019556:COS Cells / Q000166:cytology / Q000378:metabolism; D051242:Caveolin 1; D022461:Caveolins; D002451:Cell Compartmentation / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism*; D005591:Chemical Fractionation; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism; D011233:Precipitin Tests; D015398:Signal Transduction; D018411:Spodoptera / Q000166:cytology
D051242:Caveolin 1; D022461:Caveolins; D007527:Isoenzymes; D008565:Membrane Proteins; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases