title: Multiple promoters direct expression of three AKAP12 isoforms with distinct subcellular and tissue distribution profiles.
abstract: A Kinase Anchoring Protein 12 (AKAP12; also known as src-suppressed C kinase substrate (SSeCKS) and Gravin) is a multivalent anchoring protein with tumor suppressor activity. Although expression of AKAP12 has been examined in a number of contexts, its expression control remains to be elucidated. Herein, we characterize the genomic organization of the AKAP12 locus, its regulatory regions, and the spatial distribution of the proteins encoded by the AKAP12 gene. Using comparative genomics and various wet-lab assays, we show that the AKAP12 locus is organized as three separate transcription units that are governed by non-redundant promoters coordinating distinct tissue expression profiles. The proteins encoded by the three AKAP12 isoforms (designated alpha, beta, and gamma) share >95% amino acid sequence identity but differ at their N termini. Analysis of the targeting of each isoform reveals distinct spatial distribution profiles. An N-terminal myristoylation motif present in AKAP12alpha is shown to be necessary and sufficient for targeted expression of this AKAP12 isoform to the endoplasmic reticulum, a novel subcellular compartment for AKAP12. Our results demonstrate heretofore unrecognized complexity within the AKAP12 locus and suggest a mechanism for genetic control of signaling specificity through distinct regulation of alternately targeted anchoring protein isoforms.
authors.affiliation: Center for Cardiovascular Research in the Aab Institute of Biomedical Sciences, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, USA.
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Streb
authors.forename: Chad M
authors.initials: CM
authors.lastname: Kitchen
authors.forename: Irwin H
authors.initials: IH
authors.lastname: Gelman
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Miano
mesh_terms: D016475:3T3 Cells; D054758:A Kinase Anchor Proteins; D020816:Amino Acid Motifs; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D019556:COS Cells; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000235:genetics*; D002460:Cell Line; D018076:DNA, Complementary / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D015723:Gene Library; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000737:chemistry; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D008934:Mitogens / Q000737:chemistry* / Q000235:genetics*; D008969:Molecular Sequence Data; D019814:Myristic Acid / Q000737:chemistry; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012689:Sequence Homology, Nucleic Acid; D015398:Signal Transduction; D013997:Time Factors; D014018:Tissue Distribution; D014158:Transcription, Genetic
chemical_list: D054758:A Kinase Anchor Proteins; C491161:Akap12 protein, mouse; C102361:Akap12 protein, rat; D018797:Cell Cycle Proteins; D018076:DNA, Complementary; D008934:Mitogens; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D019814:Myristic Acid; D049452:Green Fluorescent Proteins; D008156:Luciferases