Arginase II activity regulates cytosolic Ca 2+ level in a p32-dependent manner that contributes to Ca 2+ -dependent vasoconstriction in native low-density lipoprotein-stimulated vascular smooth muscle cells

• Published in: Experimental & molecular medicine 2019-06, Vol.51 (6), p.1
• Main Authors: Koo, Bon-Hyeock, Hong, Dongeui, Hong, Hyeon Don, Lim, Hyun Kyo, Hoe, Kwang Lae, Won, Moo-Ho, Kim, Young Myeong, Berkowitz, Dan E, Ryoo, Sungwoo
• Format: Article
• Language: English
• Subjects: Animals; Arginase - metabolism; Carrier Proteins - metabolism; Cell Line; Cytosol - metabolism; Humans; Lipoproteins, LDL - metabolism; Male; Mice; Mice, Inbred C57BL; Mitochondrial Proteins - metabolism; Muscle, Smooth, Vascular - cytology; Muscle, Smooth, Vascular - physiology; Myocytes, Smooth Muscle - cytology; Myocytes, Smooth Muscle - metabolism; Vasoconstriction
• ISSN: 2092-6413
• DOI: 10.1038/s12276-019-0262-y

Although arginase II (ArgII) is abundant in mitochondria, Ca -accumulating organelles, the relationship between ArgII activity and Ca translocation into mitochondria and the regulation of cytosolic Ca signaling are completely unknown. We investigated the effects of ArgII activity on mitochondrial Ca uptake through mitochondrial p32 protein (p32m) and on CaMKII-dependent vascular smooth muscle cell (VSMC) contraction. Native low-density lipoprotein stimulation induced an increase in [Ca ]m as measured by CoCl -quenched calcein-AM fluorescence, which was prevented by Arg inhibition in hAoSMCs and reduced in mAoSMCs from ArgII mice. Conversely, [Ca ]c analyzed with Fluo-4 AM was increased by Arg inhibition and ArgII gene knockout. The increased [Ca ]c resulted in CaMKII and MLC 20 phosphorylation, which was associated with enhanced vasoconstriction activity to phenylephrine (PE) in the vascular tension assay. Cy5-tagged siRNA against mitochondrial p32 mRNA (sip32m) abolished mitochondrial Ca uptake and induced activation of CaMKII. Spermine, a polyamine, induced mitochondrial Ca uptake and dephosphorylation of CaMKII and was completely inhibited by sip32m incubation. In mAoSMCs from ApoE-null mice fed a high-cholesterol diet (ApoE +HCD), Arg activity was increased, and spermine concentration was higher than that of wild-type mice. Furthermore, [Ca ]m and p32m levels were elevated, and CaMKII phosphorylation was reduced in mAoSMCs from ApoE +HCD. In vascular tension experiments, an attenuated response to vasoconstrictors in de-endothelialized aorta from ApoE +HCD was recovered by incubation of sip32m. ArgII activity-dependent production of spermine augments Ca transition from the cytosol to the mitochondria in a p32m-dependent manner and regulates CaMKII-dependent constriction in VSMCs.