Mitochondrial A-kinase anchoring proteins in cardiac ventricular myocytes.

Rinzhin T Sherpa,Karni S Moshal,Michael W Rudokas,Adam Wadsworth,Shailesh R Agarwal,Chase Fiore,Robert D Harvey

doi:10.14814/phy2.15015

Rinzhin T Sherpa, Karni S Moshal + Show 5 more

Open Access

https://doi.org/10.14814/phy2.15015

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Journal: Physiological reports	Publication Date: Sep 1, 2021
Citations: 5	License type: CC BY 4.0

Affiliation: University of Nevada Reno

Abstract

Compartmentation of cAMP signaling is a critical factor for maintaining the integrity of receptor‐specific responses in cardiac myocytes. This phenomenon relies on various factors limiting cAMP diffusion. Our previous work in adult rat ventricular myocytes (ARVMs) indicates that PKA regulatory subunits anchored to the outer membrane of mitochondria play a key role in buffering the movement of cytosolic cAMP. PKA can be targeted to discrete subcellular locations through the interaction of both type I and type II regulatory subunits with A‐kinase anchoring proteins (AKAPs). The purpose of this study is to identify which AKAPs and PKA regulatory subunit isoforms are associated with mitochondria in ARVMs. Quantitative PCR data demonstrate that mRNA for dual specific AKAP1 and 2 (D‐AKAP1 & D‐AKAP2), acyl‐CoA‐binding domain‐containing 3 (ACBD3), optic atrophy 1 (OPA1) are most abundant, while Rab32, WAVE‐1, and sphingosine kinase type 1 interacting protein (SPHKAP) were barely detectable. Biochemical and immunocytochemical analysis suggests that D‐AKAP1, D‐AKAP2, and ACBD3 are the predominant mitochondrial AKAPs exposed to the cytosolic compartment in these cells. Furthermore, we show that both type I and type II regulatory subunits of PKA are associated with mitochondria. Taken together, these data suggest that D‐AKAP1, D‐AKAP2, and ACBD3 may be responsible for tethering both type I and type II PKA regulatory subunits to the outer mitochondrial membrane in ARVMs. In addition to regulating PKA‐dependent mitochondrial function, these AKAPs may play an important role by buffering the movement of cAMP necessary for compartmentation.

Highlights

Many different G protein-coupled receptors are linked to the production of cyclic adenosine monophosphate, a diffusible second messenger involved in regulating a multitude of responses in a variety of cell types
Our results suggest that D-AKAP1, D-AKAP2, acyl-CoA-binding domain-containing 3 (ACBD3), and optic atrophy 1 (OPA1) co-localize with the mitochondria to a high degree
Compartmentation of cyclic adenosine monophosphate (cAMP) signaling is critical for maintaining the integrity of receptor-specific responses, and it has been hypothesized that slow diffusion of cAMP, independent of PDE activity, plays an important role in that process (Agarwal et al, 2016; Feinstein et al, 2012; Iancu et al, 2007; Lohse et al, 2017; Saucerman et al, 2006, 2014; Yang et al, 2016; Zhang et al, 2020)

Summary

| INTRODUCTION

Many different G protein-coupled receptors are linked to the production of cyclic adenosine monophosphate (cAMP), a diffusible second messenger involved in regulating a multitude of responses in a variety of cell types. The segregation of receptors into distinct membrane domains or subcellular locations contributes to differences in the compartmentation of cAMP produced by β1 and β2-adrenergic receptors (Agarwal et al, 2011; MacDougall et al, 2012; Nikolaev et al, 2006; Rudokas et al, 2021) as well as β1ARs and E-type prostaglandin receptors (Agarwal et al, 2011; Buxton & Brunton, 1983; Rochais et al, 2006; Warrier et al, 2007). All PKA regulatory subunit isoforms are associated with mitochondria, highlighting the importance of considering all isoforms when studying PKA-dependent cAMP buffering in ARVMs

| MATERIALS AND METHODS

| RESULTS

| DISCUSSION

Findings

| Conclusion