TRPV2 channels mediate insulin secretion induced by cell swelling in mouse pancreatic β-cells

Abstract

β-Cell swelling induces membrane depolarization, which has been suggested to be caused at least partly by the activation of cation channels. Here, we show the identification of the cation channels. In isolated mouse pancreatic β-cells, the exposure to 30% hypotonic solution elicited an increase in cytosolic Ca2+ concentration ([Ca2+]c). The [Ca2+]c elevation was partially inhibited by ruthenium red, a blocker of several Ca2+-permeable channels including transient receptor potential vanilloid receptors [transient receptor potential cation channel subfamily V (TRPV)], and by nicardipine, but not by the depletion of intracellular Ca2+ stores with thapsigargin and caffeine. The hypotonic stimulation also increased insulin secretion from isolated mouse islets, which was significantly suppressed by ruthenium red. Expression of TRPV2 and TRPV4 was confirmed in mouse pancreatic islets and the MIN6 β-cell line by RT-PCR, Western blot, and immunohistochemical analyses. However, neither 4α-phorbol 12,13-didecanoate nor GSK1016790A, TRPV4 activators, showed any apparent effect on [Ca2+]c in isolated mouse β-cells or in MIN6 cells. In contrast, probenecid, a TRPV2 activator, induced an increase in [Ca2+]c in MIN6 cells, which was attenuated by ruthenium red. Moreover, the [Ca2+]c elevation induced by 30% hypotonic stimulation was significantly reduced by knockdown of TRPV2 with siRNA and by tranilast, a TRPV2 inhibitor. The knockdown of TRPV2 also decreased insulin secretion induced by the hypotonic stimulation. In addition, glucose-stimulated insulin secretion was also significantly reduced in the TRPV2-knockdown MIN6 cells. These results suggest that osmotic cell swelling activates TRPV2 in mouse β-cells, thereby causing membrane depolarization and subsequent activation of voltage-dependent Ca2+ channels and insulin secretion.

Molecular Regulations and Functions of the Transient Receptor Potential Channels of the Islets of Langerhans and Insulinoma Cells

“…TRPV2 is not expressed in human β-cells but is expressed in the non-β-cells of human islets [7]. In isolated mouse β-cells and MIN6 cells, glucose-induced osmotic cell swelling activates TRPV2 leading to membrane depolarization and insulin secretion [130]. TRPV2 also displays some spontaneous activity and contributes to the background depolarizing current.…”

“…TRPV5 is not present in human islets, but TRPV6 is expressed in the non-β-cells of human islets, which are mostly the α-cells [7]. It is expressed in the α-cells of mouse islets, rat β-cells, MIN6 cells, and INS-1E cells [130,138]. In INS-1E cells Ca 2+ influx through the TRPV6 channel regulates insulin gene expression, cell viability, and cell proliferation [138].…”

TRPV2 interaction with small molecules and lipids revealed by cryo-EM

“…TRPV2 has been shown to play a significant role in maintaining physiological cardiomyocyte function, with a potential therapeutic use of TRPV2 blockade in cardiomyopathy 4–6 . TRPV2 is required for phagocytosis in macrophages 7,8 and has also been shown to be crucial for insulin secretion in pancreatic β-cells 9,10 . Beyond its routine functions in healthy cells, TRPV2 has been shown to play a significant role in different forms of cancer 11 .…”

Polymodal Sensory Transduction in Mouse Corneal Epithelial Cells

“… 52 – 54 Given that Pannexin1 (Pnx1) hemichannels are activated by intracellular calcium, permeable to ATP and may functionally couple to TRPV4, 52 we evaluated ATP release in the presence of probenecid, at the concentration (50 µM) that blocks hemichannels without affecting gap junctional coupling or TRPV2 activation. 55 – 58 As shown in Figures 9 A, 9 B, GSK101-evoked increases in extracellular [ATP] were reduced in the presence of probenecid from 1.29 ± 0.00 to 0.89 ± 0.01 ( P < 0.001). We tested the possibility that TRPV4-mediated ATP release involves purinergic autofeedback 59 but the bioluminescence signal intensity in the presence of the P2 receptor blocker suramin (100 µM) was 1.31 ± 0.09, not significantly different from the GSK101-alone cohort.…”