Novel Calcium Signaling Nanodomains in Vascular Smooth Muscle Cells

Smooth muscle Ca2+ signaling mechanisms are crucial regulators of arterial contraction and blood pressure. Abnormalities in arterial smooth muscle cell (SMC) Ca2+ signaling mechanisms have been linked to vasoconstriction, vascular remodeling, and blood pressure elevation in hypertension. Therefore, identifying a new Ca2+ signaling mechanism could provide fresh impetus for designing novel therapeutic targets that lower blood pressure in hypertension. In this regard, TRPV4 (transient receptor potential vanilloid 4) ion channels are a well-known Ca2+-influx pathway in SMCs. Using smooth muscle-specific TRPV4-knockout mice, we provided first evidence that SMC TRPV4 channels increase resting blood pressure and contribute to blood pressure elevation in hypertension. Moreover, our preliminary data demonstrate two TRPV4 channel-containing signaling nanodomains in SMCs with opposite functional effects: (1) constrictor nanodomains involving nerve stimulation-induced activation of α1 adrenergic receptors (α1ARs)–protein kinase C (PKC)-anchoring protein AKAP150–TRPV4 channel signaling; and (2) dilator nanodomains activated by intraluminal pressure and comprising caveolin-1 scaffolded Piezo1–TRPV4–Ca2+- activated K+ (BK) channel signaling. Further, we show that constrictor α1AR–TRPV4 channel signaling is accentuated in arteries from a mouse model of hypertension and hypertensive patients, whereas dilator TRPV4–BK channel signaling is reduced. We hypothesize that miscommunication between the signaling elements disrupts the balance between constrictor and dilator signaling nanodomains and leads to blood pressure elevation in hypertension. In Aim 1, we will use smooth muscle-specific knockout mice, protein co-localization, patch-clamp electrophysiology, and blood pressure radiotelemetry to determine the molecular mechanisms underlying the excessive activation of constrictor α1AR:AKAP150:PKC:TRPV4 nanodomains in hypertension. In Aim 2, we will determine the molecular mechanisms responsible for the reduced activity of dilator Piezo1:TRPV4:BK channel nanodomains scaffolded by caveolin-1 in hypertension. The clinical relevance of studies in each Aim will be established by experiments in arteries from non-hypertensive and hypertensive individuals. Collectively, the proposed studies will establish novel SMC Ca2+-signaling nanodomains that control blood pressure and identify specific impairments at these nanodomains in hypertension.