Role of AKAP79 in â1‐Adrenergic receptor resensitization and recycling

Abstract

AKAPs (A‐kinase anchoring proteins) have been shown to participate in macromolecular signaling complexes that include protein kinases, phosphodiesterases, ion channels, and also GPCRs. In this study, we examine the role of AKAP79 (also known as AKAP79/150) in the trafficking of β1‐Adrenergic Receptor in vitro in HEK‐293 cells and in neonatal cardiac myocytes derived from AKAP150 homozygous knock out mice.Selective down regulation of AKAP79 in HEK‐293 cells and in rat neonatal cardiac myocytes, inhibited the recycling of the WT β1‐AR in HEK‐293 cells and the reintroduction of siRNA‐resistant AKAP79 rescued the recycling of the agonist‐internalized β1‐AR. Furthermore, in neonatal ventricular myocytes derived from AKAP150−/− mice or from AKAP150+/+ the β1‐AR was internalized, but did not recycle in myocytes from AKAP150−/− mice. The recycling of the β1‐AR was rescued by AKAP79, indicating that AKAP79 was required for the recycling of the β1‐AR to occur and shows that these studies across a spectrum of different cells yielded the same result. In addition we tested the effect of three different truncated mutants of AKAP79, namely AKAP79 [1–360] (ΔPKA‐binding site), AKAP79 [115–412] (Δmembrane and PKC binding domains] and AKAP79 [ΔPIX] (Δcalcineurin‐binding domain] their ability to recapitulate the effect of full‐length AKAP79 on recycling of the β1‐AR in AKAP79‐knock down cells. Immunopricipitation data showed that the interaction between the mutants and β1‐AR remained unchanged. However, none of these AKAP79 mutants was capable of rescuing the recycling of the β1‐AR in HEK‐cells, indicating the entire molecule of AKAP79/150 was required for this effect. Funded by NIH HL‐085848.