AKAP150 and Caveolin 1 Facilitate the Formation of Distinct TRPV4 Signaling Microdomains in Vascular Smooth Muscle Cells

Abstract

Ca2+ influx through transient receptor potential vanilloid 4 (TRPV4) channel is a well-established pathway in vascular smooth muscle cells (SMCs). We recently discovered two separate SMC TRPV4 (TRPV4SMC) channel subpopulations: constrictor TRPV4SMC channels that are activated by α1 adrenergic receptors (a1AR) through protein kinase C (PKC), and dilator TRPV4SMC channels that are activated by intraluminal pressure and couple with Ca2+-activated K+ (BK) channels. However, the underlying mechanism for the formation of these TRPV4SMC signaling microdomains is unclear. AKAP150 (A kinase anchoring protein 150), a PKC-anchoring protein, is essential for PKC activation of TRPV4SMC channels, and Caveolin-1 (Cav1) has been linked to enhanced activity of TRPV4 and BK channels. We hypothesized that distinct anchoring proteins facilitate the formation of spatially separated TRPV4SMC signaling microdomains. Therefore, we tested the possibility that AKAP150 mediates α1AR-induced activation of constrictor TRPV4SMC channels, and Cav1 provides a signaling scaffold for the intraluminal pressure-activated TRPV4SMC-BK channel signaling. Radiotelemetric recordings showed lower resting blood pressure in tamoxifen-inducible, SMC-specific AKAP150KO (AKAP150SMCKO) mice, suggesting that AKAP150SMC increases the resting blood pressure. On the contrary, Cav1SMCKO mice showed elevated resting blood pressure, suggesting that Cav1SMC decreases blood pressure. Furthermore, phenylephrine (PE, a1AR agonist)-induced TRPV4SMC currents and increase in blood pressure (1 mg/kg PE, intraperitoneal), and nerve stimulation-induced (electrical pulses; 50–150 V, 0.25-ms pulse, 15 Hz) TRPV4SMC channel activity were absent in AKAP150SMCKO mice, but not in Cav1SMCKO mice. TRPV4 channel-activated BK current was abrogated in SMCs from Cav1SMCKO mice, but not in SMCs from AKAP150SMCKO mice. Together, these data supported the concept that AKAP150 and Cav1 are required for the formation of constrictor and dilator TRPV4SMC signaling microdomains, respectively. Studies in other cell types have shown that mechanosensitive Piezo1 channels can increase the activity of TRPV4 channels. Therefore, we determined whether Piezo1 is required for intraluminal pressure- activation of the dilator TRPV4SMC channels. We postulated that intraluminal-pressure activates Cav1-scaffolded Piezo1SMC-TRPV4SMC-BK channel signaling. Piezo1SMCKO mice showed a loss of intraluminal pressure-induced TRPV4SMC channel activity and increased myogenic constriction in MAs. Importantly, Yoda1 (Piezo1 activator)-induced increase in BK current was absent in SMCs from Cav1SMCKO, TRPV4SMCKO, and Piezo1SMCKO mice, but not AKAP150SMCKO mice. Together, our results suggest that AKAP150SMC and Cav1SMC facilitate constrictor α1AR-PKC-TRPV4SMC and dilator Piezo1SMC-TRPV4SMC-BK channel signaling, respectively. Collectively, our data identify the anchoring proteins involved in the formation of distinct Ca2+ signaling microdomains with opposite effects on blood pressure. This work was supported by funding from the American Heart Association to YLC (POST833691), the National Institutes of Health to SKS (HL146914, HL142808, and HL147555). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.