A-kinase-anchoring protein 1 (dAKAP1)-based signaling complexes coordinate local protein synthesis at the mitochondrial surface

Laura Gabrovsek,Kerrie B Collins,Stacey Aggarwal,Lauren M Saunders,Ho-Tak Lau,Danny Suh,Yasemin Sancak,Cole Trapnell,Shao-En Ong,F Donelson Smith,John D Scott

doi:10.1074/jbc.ra120.013454

Laura Gabrovsek, Kerrie B Collins + Show 9 more

Open Access

https://doi.org/10.1074/jbc.ra120.013454

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Abstract

Compartmentalization of macromolecules is a ubiquitous molecular mechanism that drives numerous cellular functions. The appropriate organization of enzymes in space and time enables the precise transmission and integration of intracellular signals. Molecular scaffolds constrain signaling enzymes to influence the regional modulation of these physiological processes. Mitochondrial targeting of protein kinases and protein phosphatases provides a means to locally control the phosphorylation status and action of proteins on the surface of this organelle. Dual-specificity protein kinase A anchoring protein 1 (dAKAP1) is a multivalent binding protein that targets protein kinase A (PKA), RNAs, and other signaling enzymes to the outer mitochondrial membrane. Many AKAPs recruit a diverse set of binding partners that coordinate a broad range of cellular processes. Here, results of MS and biochemical analyses reveal that dAKAP1 anchors additional components, including the ribonucleoprotein granule components La-related protein 4 (LARP4) and polyadenylate-binding protein 1 (PABPC1). Local translation of mRNAs at organelles is a means to spatially control the synthesis of proteins. RNA-Seq data demonstrate that dAKAP1 binds mRNAs encoding proteins required for mitochondrial metabolism, including succinate dehydrogenase. Functional studies suggest that the loss of dAKAP1-RNA interactions reduces mitochondrial electron transport chain activity. Hence, dAKAP1 plays a previously unappreciated role as a molecular interface between second messenger signaling and local protein synthesis machinery.

Highlights

Spatial and temporal transmission of intracellular messages often involves anchoring and scaffolding proteins [1]
We show that Dual-specificity protein kinase A anchoring protein 1 (dAKAP1) interacts with several components of ribonucleoprotein granules, the intracellular substructures composed of RNA and proteins that participate in mRNA translation, storage, and decay
A common feature of anchoring proteins is a modular organization in which structured protein interaction domains are linked by regions of intrinsic disorder [1, 20, 21]. dAKAP1

Summary

Introduction

Spatial and temporal transmission of intracellular messages often involves anchoring and scaffolding proteins [1]. DAKAP1 controls localized protein translation contains four identifiable domains: a mitochondrial targeting domain (MTD; residues 1–29); the PKA-anchoring helix (residues 348–359); a KH domain (residues 607–671) that binds RNA; and a Tudor domain (residues 707–817), a module that is known to recognize methylated arginine residues [22] (Fig. 1A). Immunofluorescent staining of WT cells revealed a distribution of dAKAP1 (green) signal that localized to the mitochondria (as indicated by the mitochondrial marker MitoTracker, deep red; Fig. 1C and the higher magnification inset).

Results

Conclusion