(35) DUAL-SPECIFIC A KINASE ANCHORING PROTEINS TARGET MITOCHONDRIA

G. Perkins¹, M. Mackey¹, M. Martone¹, L. Wang², S. Taylor² and M. Ellisman^1
1National Center for Microscopy and Imaging Research, University of California, San Diego, La Jolla, CA 92093-0608.
²Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0654.

Protein kinases are enzymes that alter the phosphorylation state of cellular target proteins. The targets are ubiquitous and involved in hormone-mediated events ranging from cell growth to cell death. Cyclic AMP-dependent protein kinase (PKA) is a specific protein kinase that is part of the signaling pathway of cAMP. We are investigating compartmentation of PKA with A-kinase anchoring proteins (AKAPs) using confocal immunofluorescence microscopy and immunoelectron microscopy. Specificity in cellular responses to cAMP is thought to reflect differences in subcellular localization of AKAPs. DAKAPs are novel dual-specific AKAPs in that they can bind to either RI or RII isoforms of PKA. There are two types, DAKAP-1 and DAKAP-2. Our objective is to ascertain which regulatory subunits of PKA associate with DAKAPs based on labeling patterns at three levels: tissue type, cell type, and subcellular localization, e.g., organelles. We found that DAKAP-1 and DAKAP-2 associate differentially with mitochondria in specific types of brain cells. By using multifluorescent labeling, we have determined the patterns of co-distribution of these DAKAPs with RI and RII subunits to better understand the physiological partners.

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