Protein kinase D activation induces mitochondrial fragmentation and dysfunction in cardiomyocytes

Abstract

Regulation of mitochondrial morphology is crucial for the maintenance of physiological functions in many cell types including cardiomyocytes. Small and fragmented mitochondria are frequently observed in pathological conditions, but it is still unclear which cardiac signalling pathway is responsible for regulating the abnormal mitochondrial morphology in cardiomyocytes. Here we demonstrate that a downstream kinase of G protein-coupled receptor (G PCR) signalling, protein kinase D (PKD), mediates pathophysiological modifications in mitochondrial morphology and function, which consequently contribute to the activation of apoptotic signalling. We show that G PCR stimulation induced by α -adrenergic stimulation mediates mitochondrial fragmentation in a fission- and PKD-dependent manner in H9c2 cardiac myoblasts and rat neonatal cardiomyocytes. Upon G PCR stimulation, PKD translocates from the cytoplasm to the outer mitochondrial membrane (OMM) and phosphorylates a mitochondrial fission protein, dynamin-like protein 1 (DLP1), at S637. PKD-dependent phosphorylation of DLP1 initiates DLP1 association with the OMM, which then enhances mitochondrial fragmentation, mitochondrial superoxide generation, mitochondrial permeability transition pore opening and apoptotic signalling. Finally, we demonstrate that DLP1 phosphorylation at S637 by PKD occurs in vivo using ventricular tissues from transgenic mice with cardiac-specific overexpression of constitutively active Gα protein. In conclusion, G PCR-PKD signalling induces mitochondrial fragmentation and dysfunction via PKD-dependent DLP1 phosphorylation in cardiomyocytes. This study is the first to identify a novel PKD-specific substrate, DLP1 in mitochondria, as well as the functional role of PKD in cardiac mitochondria. Elucidation of these molecular mechanisms by which PKD-dependent enhanced fission mediates cardiac mitochondrial injury will provide novel insight into the relationship among mitochondrial form, function and G PCR signalling.

RhoA regulates Drp1 mediated mitochondrial fission through ROCK to protect cardiomyocytes

“…This contrasts with a study using podocytes subjected to hyperglycemia where ROCK was implicated in phosphorylation of Drp1 at serine-637 [37]. PKD, another downstream target of RhoA explored in our previous work [3, 9, 10], has also been suggested to phosphorylate Drp1 at serine-637 in cardiomyocytes [38]. However, serine-637 phosphorylation of Drp1 was not affected by activation of RhoA nor was the RhoA-induced increase in phosphorylation of Drp1 at serine-616 blocked by a PKD inhibitor (data not shown).…”

Calpains play an essential role in mechanical ventilation-induced diaphragmatic weakness and mitochondrial dysfunction

“…This is potentially important because calpain-induced cleavage of PKC-δ results in a catalytically active protein with higher PKC-δ enzymatic activity [ 34 , 35 ]. While the role of PKC-δ in skeletal muscle is not well defined, evidence from other cell types confirms that PKC-δ promotes mitochondrial dysfunction by increasing mitochondrial ROS production, mitochondrial fission, mitochondrial permeable transition pore opening, and cytochrome C release [ [50] , [51] , [52] , [53] , [54] ]. For example, the cleaved PKC-δ fragment has been reported to interact with the mitochondrial fission protein DRP1 and translocate to mitochondria resulting in increased mitochondrial fission [ 53 , 54 ].…”

Magnesium supplementation improves diabetic mitochondrial and cardiac diastolic function

“…Fifteen to 24 images were taken randomly from 3-5 mice in each group. To analyze the mitochondrial structure, we measured the mitochondrial area and gray mean intensity of each single mitochondrion in all images by ImageJ (NIH) (44,45).…”