AKAP350, a multiply spliced protein kinase A-anchoring protein associated with centrosomes

Protein kinase A-anchoring proteins (AKAPs) localize the second messenger r esponse to particular subcellular domains by sequestration of the type II p rotein kinase A. Previously, AKAP120 was identified from a rabbit gastric p arietal cell cDNA library; however, a monoclonal antibody raised against AK AP120 labeled a 350-kDa band in Western blots of parietal cell cytosol, Rec loning has now revealed that AKAP120 is a segment of a larger protein, AKAP 350, We have now obtained a complete sequence of human gastric AKAP350 as w ell as partial cDNA sequences from human lung and rabbit parietal cells. Th e genomic region containing AKAP350 is found on chromosome 7q21 and is mult iply spliced, producing at least three distinct AKAP350 isoforms as well as yotiao, a protein associated with the N-methyl-D-aspartate receptor, Rabbi t parietal cell AKAP350 is missing a sequence corresponding to a single exo n in the middle of the molecule located just after the yotiao homology regi on. Two carboxyl-terminal splice variants were also identified. Both of the major splice variants showed tissue- and cell-specific expression patterns . Immunofluorescence microscopy demonstrated that AKAP350 was associated wi th centrosomes in many cell types. In polarized Madin-Darby canine kidney c ells, AKAP350 localized asymmetrically to one pole of the centrosome, and n ocodazole did not alter its localization. During the cell cycle, AKAP350 wa s associated with the centrosomes as well as with the cleavage furrow durin g anaphase and telophase, Several epithelial cell types also demonstrated n oncentrosomal pools of AKAP350, especially parietal cells, which contained multiple cytosolic immunoreactive foci throughout the cells. The localizati on of AKAP350 suggests that it may regulate centrosomal and noncentrosomal cytoskeletal systems in many different cell types.