Calcineurin-independent regulation of plasma membrane Ca²⁺ ATPase-4 in the vascular smooth muscle cell cycle

Abstract

. Calcineurinindependent regulation of plasma membrane Ca 2ϩ ATPase-4 in the vascular smooth muscle cell cycle. Am J Physiol Cell Physiol 285: C88-C95, 2003; 10.1152/ajpcell.00518.2002.-Calcineurin mediates repression of plasma membrane Ca 2ϩ -ATPase-4 (PMCA4) expression in neurons, whereas c-Myb is known to repress PMCA1 expression in vascular smooth muscle cells (VSMC). Here, we describe a novel mouse VSMC line (MOVAS) in which 45 Ca efflux rates decreased 50%, fura 2-AM-based intracellular Ca 2ϩ concentrations ([Ca 2ϩ ]i) increased twofold, and real-time RT-PCR and Western blot revealed a ϳ40% decrease in PMCA4 expression levels from G 0 to G1/S in the cell cycle, where PMCA4 constituted ϳ20% of total PMCA protein. Although calcineurin activity increased fivefold as MOVAS progressed from G0 to G1/S, inhibition of this increase with either BAPTA or retroviral transduction with peptide inhibitors of calcineurin (CAIN), or its downstream target nuclear factor of activated T cells (NFAT) (VIVIT), had no effect on the repression of PMCA4 mRNA expression at G1/S. By contrast, Ca 2ϩ -independent activity of the calmodulin-dependent protein kinase-II (CaMK-II) increased eightfold as MOVAS progressed from G0 to G1/S, and treatment with an inhibitor of CaMK-II (KN-93) or transduction of a c-Myb-neutralizing antibody significantly alleviated the G1/S-associated repression of PMCA4. These data show that G1/S-specific PMCA4 repression in proliferating VSMC is brought about by c-Myb and CaMK-II and that calcineurin may regulate cell cycle-associated [Ca 2ϩ ]i through alternate targets. /calmodulin-mediated signals act at multiple points in the cell cycle, including the G 0 /G 1 transition, the initiation of S-phase, and the initiation and completion of M phase (reviewed in Refs. 4,31,38,and 44 ] i ) needed for G 1 -to-S transitions in rat vascular smooth muscle cells (VSMC) (22, 23).We previously showed that the cell cycle-associated repression of PMCA1 expression during G 0 to G 1 /S progression in rat VSMC is mediated by the c-Myb transcription factor (1). However, the mechanism(s) underlying the cell cycle-associated repression of PMCA4 had not been elucidated. Guerini et al. (18) demonstrated in mouse neurons that PMCA4 expression can be repressed by a calcineurin-dependent pathway. Given this result, we hypothesized that G 1 /Sassociated repression of PMCA4 expression in VSMC may also be mediated by calcineurin. To explore these mechanisms in cell culture, we generated a clonal, immortalized mouse VSMC line (MOVAS). Immunostaining for smooth muscle-specific proteins such as SM22␣, calponin, smooth muscle-specific ␣-actin and desmin, as well as SM22␣ promoter-driven enhanced green fluorescent protein (EGFP) expression, confirm the lineage and phenotype of these cells. 45 Ca efflux assays and fura 2-based ratiometric Ca 2ϩ imaging reveal regulated Ca 2ϩ efflux and [Ca 2ϩ ] i at the G 1 /S transition point. Western blot and real time RT-PCR reveal cell cycle-regulated repression of mouse PMCA1 and PMCA4. Drugs in...

Recapitulation of two genomewide association studies on blood pressure and essential hypertension in the Korean population

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Genetic variations in ATP2B1, CSK, ARSG and CSMD1 loci are related to blood pressure and/or hypertension in two Korean cohorts

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Intravenous immunoglobulin and salicylate differentially modulate pathogenic processes leading to vascular damage in a model of Kawasaki disease

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