Characterization and chromosomal localization of the human homologue of a rat AMP-activated protein kinase-encoding gene: a major regulator of lipid metabolism in mammals

AMP-activated protein kinase (AMPK) phosphorylates and inactivates acetyl-CoA carboxylase and β-hydroxy β-methylglutaryl-coenzyme A (HMG-CoA) reductase which are the major enzymes involved in fatty acid and lipid biosyntheses. The AMPK gene from rat ( rAMPK ) has recently been cloned [Carling et al. J. Biol. Chem. 269 (1994) 11442–11448]. In order to study the structure and function of the human AMPK gene (h AMPK ), we have cloned the gene, and report in this communication its nucleotide (nt) sequence, tissue distribution and chromosomal location. Our results show that the ORF of h AMPK encodes 552 amino acids (aa) (62.250 kDa) and is highly conserved with r ampk with identities of 97.3 and 90% at the aa and nt levels, respectively. The h AMPK gene bears homology to a yeast protein kinase-encoding gene ( snf 1) that regulates carbohydrate metabolism, and also with three other genes encoding SNFl-like kinases from different plant species, namely Arabidopsis thaliana, Hordeum vulgare and Secale cereale. As determined by fluorescent in situ hybridization of a human metaphase chromosome spread, h AMPK maps to chromosome lp31. The size of the h AMPK transcript is 8.5 kb and the transcription start point ( tsp ) is located approx. 46 bp upstream from the ATG codon. While 10–15% of AMPK is alternatively spliced in most tissues of the rat, our RT-PCR analyses of the h AMPK mRNA did not reveal the presence of any alternatively spliced form of the gene in human tissues. An interesting aspect of AMPK is that its expression, unlike in rat liver, could not be detected in human liver, and thus the purported role of the gene in controlling fatty-acid synthesis in the human liver remains to be determined.