title: Non-catalytic beta- and gamma-subunit isoforms of the 5'-AMP-activated protein kinase.
abstract: The mammalian 5'-AMP-activated protein kinase (AMPK) is a heterotrimeric protein consisting of alpha-, beta-, and gamma-subunits. The alpha-subunit is the catalytic subunit and is related to the yeast Snf1p kinase. In this study, we report the cloning of full-length cDNAs for the non-catalytic beta- and gamma-subunits. The rat liver AMPK beta-subunit clone predicts a protein of 30,464 Da, which is related to the Sip1p, Sip2p, and Gal83p subfamily of yeast proteins that interact with Snf1p and are involved in glucose regulation of gene expression. The AMPK beta-subunit, when expressed in bacteria and in mammalian cells, migrates anomalously on SDS gels at an apparent molecular mass of 40 kDa. Rat and human liver AMPK gamma-subunit clones predict a protein of 37,577 Da (AMPK-gamma1), which is related to the yeast Snf4p protein that copurifies with Snf1p and to a larger family of other human AMPK gamma-isoforms. The mRNAs for both AMPK- beta and AMPK-gamma1 are widely expressed in rat tissues, consistent with a broad role for AMPK in cellular regulation. These data reveal a mammalian multisubunit protein kinase strikingly similar to the multisubunit glucose-sensing Snf1 kinase complex. The identification of isoform families for the AMPK subunits indicates the potential diversity of the roles of this highly conserved signaling system in nutrient regulation and utilization in mammalian cells.
authors.affiliation: Department of Medicine, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
authors.forename: G
authors.initials: G
authors.lastname: Gao
authors.forename: C S
authors.initials: CS
authors.lastname: Fernandez
authors.forename: D
authors.initials: D
authors.lastname: Stapleton
authors.forename: A S
authors.initials: AS
authors.lastname: Auster
authors.forename: J
authors.initials: J
authors.lastname: Widmer
authors.forename: J R
authors.initials: JR
authors.lastname: Dyck
authors.forename: B E
authors.initials: BE
authors.lastname: Kemp
authors.forename: L A
authors.initials: LA
authors.lastname: Witters
mesh_terms: D055372:AMP-Activated Protein Kinases; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins; D003001:Cloning, Molecular; D017931:DNA Primers / Q000737:chemistry; D018076:DNA, Complementary / Q000235:genetics; D015870:Gene Expression; D006801:Humans; D008099:Liver / Q000201:enzymology; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics*; D011494:Protein Kinases / Q000235:genetics*; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013552:Swine; D014157:Transcription Factors / Q000235:genetics
chemical_list: D002352:Carrier Proteins; D017931:DNA Primers; D018076:DNA, Complementary; D009097:Multienzyme Complexes; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D011494:Protein Kinases; C526222:PRKAG1 protein, human; D017346:Protein Serine-Threonine Kinases; C078651:SNF4 protein, S cerevisiae; D055372:AMP-Activated Protein Kinases