Myotonic dystrophy protein kinase (DMPK) prevents ROS-induced cell death by assembling a hexokinase II-Src complex on the mitochondrial surface

Abstract

The biological functions of myotonic dystrophy protein kinase (DMPK), a serine/threonine kinase whose gene mutations cause myotonic dystrophy type 1 (DM1), remain poorly understood. Several DMPK isoforms exist, and the long ones (DMPK-A/B/C/D) are associated with the mitochondria, where they exert unknown activities. We have studied the isoform A of DMPK, which we have found to be prevalently associated to the outer mitochondrial membrane. The kinase activity of mitochondrial DMPK protects cells from oxidative stress and from the ensuing opening of the mitochondrial permeability transition pore (PTP), which would otherwise irreversibly commit cells to death. We observe that DMPK (i) increases the mitochondrial localization of hexokinase II (HK II), (ii) forms a multimeric complex with HK II and with the active form of the tyrosine kinase Src, binding its SH3 domain and (iii) it is tyrosine-phosphorylated by Src. Both interaction among these proteins and tyrosine phosphorylation of DMPK are increased under oxidative stress, and Src inhibition selectively enhances death in DMPK-expressing cells after HK II detachment from the mitochondria. Down-modulation of DMPK abolishes the appearance of muscle markers in in vitro myogenesis, which is rescued by oxidant scavenging. Our data indicate that, together with HK II and Src, mitochondrial DMPK is part of a multimolecular complex endowed with antioxidant and pro-survival properties that could be relevant during the function and differentiation of muscle fibers.

Hexokinase II integrates energy metabolism and cellular protection: Akting on mitochondria and TORCing to autophagy

“…DMPK-A forms a molecular complex with Src and HK-II at the MOM in skeletal muscle cells subjected to oxidative stress and stabilizes mitoHK-II binding to confer antioxidant protection. 135 (3) Uncoupling proteins (UCPs) are mitochondrial anion carrier proteins that mitigate mitochondrial ROS emission, probably by regulating the mitochondrial membrane potential. 136 A recent study using UCP3 KO mice showed that UCP3 enhanced mitoHK-II binding in skeletal muscle, participating in a UCP3-mediated decrease in ROS emission.…”

Metabolic reprogramming identifies the most aggressive lesions at early phases of hepatic carcinogenesis

“…The enhanced glycolytic activity of RH cells was also confirmed by their higher glucose uptake and lactate release and by an increase in the expression of both MCT4 and of the glucose transporter GLUT1, compared to RNT cells (Figure 3B-3C and Supplementary Figure S3A). In addition, the expression of Hexokinase II (HK II), the HK isoform highly induced in a variety of tumor cells [28], where it binds to mitochondria and contributes to cell survival [29, 30, 31], was much higher in RH cells than in RNT hepatocytes (Figure 3C), where HK II associated with mitochondria (Supplementary Figure S3B). In RH cells, glycolysis induction matched inhibition of OXPHOS, as demonstrated by decreased oxygen consumption rate (OCR) both in basal conditions and after maximal stimulation with the proton uncoupler carbonyl cyanide-4-(trifluoromethoxy) phenylhydrazone (FCCP) (Figure 3A, right).…”

Mitochondrial quality control: Cell-type-dependent responses to pathological mutant mitochondrial DNA

“…93 Cells were preincubated with 20 nM TMRM and 1.6 mM cyclosporine H (Enzo Life Sciences, ALX-380-286), to inhibit the nonspecific cell extrusion of the probe by P-glycoprotein, for 30 min. Cells were washed with PBS, trypsinized, centrifuged and resuspended in 300 ml of PBS.…”