A Gs-coupled purinergic receptor boosts Ca2+ influx and vascular contractility during diabetic hyperglycemia

Abstract

Elevated glucose increases vascular reactivity by promoting L-type CaV1.2 channel (LTCC) activity by protein kinase A (PKA). Yet, how glucose activates PKA is unknown. We hypothesized that a Gs-coupled P2Y receptor is an upstream activator of PKA mediating LTCC potentiation during diabetic hyperglycemia. Experiments in apyrase-treated cells suggested involvement of a P2Y receptor underlying the glucose effects on LTTCs. Using human tissue, expression for P2Y11, the only Gs-coupled P2Y receptor, was detected in nanometer proximity to CaV1.2 and PKA. FRET-based experiments revealed that the selective P2Y11 agonist NF546 and elevated glucose stimulate cAMP production resulting in enhanced PKA-dependent LTCC activity. These changes were blocked by the selective P2Y11 inhibitor NF340. Comparable results were observed in mouse tissue, suggesting that a P2Y11-like receptor is mediating the glucose response in these cells. These findings established a key role for P2Y11 in regulating PKA-dependent LTCC function and vascular reactivity during diabetic hyperglycemia.

Pannexin‐1 mediated ATP release in adipocytes is sensitive to glucose and insulin and modulates lipolysis and macrophage migration

“…However, ATP (via P2 receptors) or its degradation product adenosine (via P1 receptors) can also significantly contrib ute to its regulation in both white and brown adipocytes. 18,46 Notably, in our cells, ATP and BzATP have similar effect on calcium signals and lipolysis, indicating that the P2X7 re ceptor could mediate these processes, even though we cannot exclude a role for other P2 receptors, as reported in rat white adipocytes. 37,50 The degree of lipolysis inhibition by apyrase could be surprising, but to us, it indicates that the effect of isoproterenol on lipolysis is partially dependent on the release (and action) of endogenous ATP.…”

“…Adipocytes grown in high glucose medium, mimicking a hyperglycaemic state, displayed enhanced ATP release com pared to the normoglycaemic state. 46 Remarkably, insulin stimulation on its own did not affect ATP release, while it strongly inhib ited the adrenergically induced ATP release by stimulating the hydrolysis of cAMP via the signalling pathway that ac tivates PDE3 ( Figure 5). 46 Remarkably, insulin stimulation on its own did not affect ATP release, while it strongly inhib ited the adrenergically induced ATP release by stimulating the hydrolysis of cAMP via the signalling pathway that ac tivates PDE3 ( Figure 5).…”

“…This effect does not seem to be related with increased intracellular ATP production ( Figure 5B), but it could be mediated by a glucose-depen dent cAMP production and PKA activity as recently shown in arterial myocytes. 46 Remarkably, insulin stimulation on its own did not affect ATP release, while it strongly inhib ited the adrenergically induced ATP release by stimulating the hydrolysis of cAMP via the signalling pathway that ac tivates PDE3 ( Figure 5). This insulin-activated PDE3 sig nalling is known in various insulin-sensitive cells, including adipocytes where it inhibits lipolysis.…”

Ion Channels and Their Regulation in Vascular Smooth Muscle

“…Irrespectively of this however, PKA signaling has been generally linked with vasodilation, thus raising questions about the functional relevance, if any, of this kinase in the regulation of vascular LTCCs. Intriguingly, recent studies revealed that elevations in extracellular D-glucose (HG) potentiate LTCC activity via a G s /AC/PKA pathway in vascular smooth muscle [82][83][84][85]. This HG-induced PKA-dependent activation of LTCCs resulted in increased global [Ca 2+ ] i and vasoconstriction, thus providing the first example of a PKA-dependent pathway underlying vascular smooth muscle contraction.…”

“…The association of Ca V 1.2 with these signaling pathways is orchestrated by AKAP5 [86]. PKA (and perhaps PKC) augments L-type Ca 2+ channel Ca V 1.2 activity by increasing Ca V 1.2 phosphorylation at serine 1928 (pS 1928 ) [82,85] stochastic and persistent activity of LTCCs was modulated by membrane potential [92]. However, the occurrence of LTCCs with persistent activity is limited to specific regions of the surface membrane and has been demonstrated to be highly dependent on PKC activity and AKAP5 expression [81,86].…”