The mitochondrial targeting form of PKA anchoring protein D‐AKAP1a may affect the structure of mitochondria cristae and the function of mitochondria

Abstract

D-AKAP1 is a PKA anchoring protein that targets PKA to mitochondria or ER. After defining the N-terminal mitochondrial targeting motif, the mitochondrial targeting forms of D-AKAP1 were characterized for their localization and function. The localization of D-AKAP1 was analyzed following submitochondrial fractionation in mouse liver. Most of D-AKAP1 was detected on the outer membrane with smaller amounts on the inner membrane. This distribution pattern is consistent with the immuno-Gold EM analysis on intact mitochondria and mitoplasts, respectively. The outer membrane localization of D-AKAP1 was further confirmed using an in vitro import assay as the association of D-AKAP1 with mitochondria is resistant to high salt wash, but sensitive to proteinase. A stable cell line overexpressing a mito-targeting D-AKAP1 die in galactose medium, suggesting a deficiency in oxidative phosphorylation. No functional Complex I could be detected in these cells. EM analysis showed that these cells have tubular form of mitochondrial cristae in contrast to the lamellar form in non-transfected cells. Both the surface area and number of cristea are reduced in these cells. In summary, over-expression of D-AKAP1 affects cristae structure, and this may therefore alter mitochondria function to carry out oxidative phosphorylation. (This work was funded by the NIH DK54441, NIH P41RR004050, and by the Howard Hughes Medical Institute.)