Mechanisms underlying heterogeneous Ca2+ sparklet activity in arterial smooth muscle

Manuel F. Navedo, Gregory C. Amberg, Madeline Nieves, Jeffery D. Molkentin, Luis F. Santana

Research output: Contribution to journalArticlepeer-review

88 Scopus citations

Abstract

In arterial smooth muscle, single or small clusters of Ca2+ channels operate in a high probability mode, creating sites of nearly continual Ca2+ influx (called "persistent Ca2+ sparklet" sites). Persistent Ca2+ sparklet activity varies regionally within any given cell. At present, the molecular identity of the Ca2+ channels underlying Ca2+ sparklets and the mechanisms that give rise to their spatial heterogeneity remain unclear. Here, we used total internal reflection fluorescence (TIRF) microscopy to directly investigate these issues. We found that tsA-201 cells expressing L-type Cavα1.2 channels recapitulated the general features of Ca2+ sparklets in cerebral arterial myocytes, including amplitude of quantal event, voltage dependencies, gating modalities, and pharmacology. Furthermore, PKCα activity was required for basal persistent Ca2+ sparklet activity in arterial myocytes and tsA-201 cells. In arterial myocytes, inhibition of protein phosphatase 2A (PP2A) and 2B (PP2B; calcineurin) increased Ca2+ influx by evoking new persistent Ca2+ sparklet sites and by increasing the activity of previously active sites. The actions of PP2A and PP2B inhibition on Ca2+ sparklets required PKC activity, indicating that these phosphatases opposed PKC-mediated phosphorylation. Together, these data unequivocally demonstrate that persistent Ca2+ sparklet activity is a fundamental property of L-type Ca2+ channels when associated with PKC. Our findings support a novel model in which the gating modality of L-type Ca2+ channels vary regionally within a cell depending on the relative activities of nearby PKCα, PP2A, and PP2B.

Original languageEnglish (US)
Pages (from-to)611-622
Number of pages12
JournalJournal of General Physiology
Volume127
Issue number6
DOIs
StatePublished - Jun 2006
Externally publishedYes

ASJC Scopus subject areas

  • Physiology

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