Involvement of atypical protein kinase C in the regulation of cardiac glucose and long-chain fatty acid uptake

Daphna D J Habets,Arend Bonen,Erik A Richter,Michael Leitges,Jan F C Glatz,Joost J F P Luiken,Will A Coumans,Margriet Ouwens,Stine J Maarbjerg,Monique Vergouwe

doi:10.3389/fphys.2012.00361

Daphna D J Habets, Arend Bonen + Show 8 more

Open Access

https://doi.org/10.3389/fphys.2012.00361

Copy DOI

Abstract

Aim: The signaling pathways involved in the regulation of cardiac GLUT4 translocation/glucose uptake and CD36 translocation/long-chain fatty acid uptake are not fully understood. We compared in heart/muscle-specific PKC-λ knockout mice the roles of atypical PKCs (PKC-ζ and PKC-λ) in regulating cardiac glucose and fatty acid uptake. Results: Neither insulin-stimulated nor AMPK-mediated glucose and fatty acid uptake were inhibited upon genetic PKC-λ ablation in cardiomyocytes. In contrast, myristoylated PKC-ζ pseudosubstrate inhibited both insulin-stimulated and AMPK-mediated glucose and fatty acid uptake by >80% in both wild-type and PKC-λ-knockout cardiomyocytes. In PKC-λ knockout cardiomyocytes, PKC-ζ is the sole remaining atypical PKC isoform, and its expression level is not different from wild-type cardiomyocytes, in which it contributes to 29% and 17% of total atypical PKC expression and phosphorylation, respectively. Conclusion: Taken together, atypical PKCs are necessary for insulin-stimulated and AMPK-mediated glucose uptake into the heart, as well as for insulin-stimulated and AMPK-mediated fatty acid uptake. However, the residual PKC-ζ activity in PKC-λ-knockout cardiomyocytes is sufficient to allow optimal stimulation of glucose and fatty acid uptake, indicating that atypical PKCs are necessary but not rate-limiting in the regulation of cardiac substrate uptake and that PKC-λ and PKC-ζ have interchangeable functions in these processes.

Highlights

Glucose and long-chain fatty acids are the most important cardiac substrates
CHARACTERIZATION OF CARDIOMYOCYTES FROM protein kinase C (PKC)-λ KNOCKOUT MICE Hearts from heart/muscle-specific PKC-λ knockout mice were previously controlled for proper deletion of PKC-λ (Farese et al, 2007) using a rabbit polyclonal antibody directed against a peptide spanning residues 184-234 of the PKC-λ protein
A commercailly available antibody (Santa Cruz–C20) has been commonly used to detect PKC-λ (Farese et al, 2007; Luiken et al, 2009). This rabbit polyclonal antibody recognizes the C-terminus of atypical PKCs, which is identical for PKC-λ and PKC-ζ

Summary

Introduction

Glucose and long-chain fatty acids are the most important cardiac substrates. Both substrates are efficiently extracted from the interstitial space by substrate specific sarcolemmal transporters. GLUT4 is well-known to be the main cardiac glucose transporter It is well-established that GLUT4 translocation from recycling endosomes to the plasma membrane accounts for stimulation of cardiac glucose uptake upon physiological stimuli, especially increased contractile activity and increased circulating levels of insulin (Sevilla et al, 1997; Glatz et al, 2010). In Abbreviations: AMPK, AMP-activated protein kinase; aPKC, atypical protein kinase C; AS160, Akt substrate 160; CD36, fatty acid translocase CD36; GAPDH, glyceraldehydes-3-phosphate dehydrogenase; GLUT4, glucose transporter 4; PKC, protein kinase C; VAMP2, vesicle-associated membrane protein-2

Objectives

Methods

Results

Discussion

Conclusion