Implications of αvβ3 Integrin Signaling in the Regulation of Ca2+ Waves and Myogenic Tone in Cerebral Arteries.
OBJECTIVE
The myogenic response is central to blood flow regulation in the brain. Its induction is tied to elevated cytosolic [Ca(2+)], a response primarily driven by voltage-gated Ca(2+) channels and secondarily by Ca(2+) wave production. Although the signaling events leading to the former are well studied, those driving Ca(2+) waves remain uncertain.


RESULTS
We postulated that αvβ3 integrin signaling is integral to the generation of pressure-induced Ca(2+) waves and cerebral arterial tone. This hypothesis was tested in rat cerebral arteries using the synergistic strengths of pressure myography, rapid Ca(2+) imaging, and Western blot analysis. GRGDSP, a peptide that preferentially blocks αvβ3 integrin, attenuated myogenic tone, indicating the modest role for sarcoplasmic reticulum Ca(2+) release in myogenic tone generation. The RGD peptide was subsequently shown to impair Ca(2+) wave generation and myosin light chain 20 (MLC20) phosphorylation, the latter of which was attributed to the modulation of MLC kinase and MLC phosphatase via MYPT1-T855 phosphorylation. Subsequent experiments revealed that elevated pressure enhanced phospholipase Cγ1 phosphorylation in an RGD-dependent manner and that phospholipase C inhibition attenuated Ca(2+) wave generation. Direct inhibition of inositol 1, 4, 5-triphosphate receptors also impaired Ca(2+) wave generation, myogenic tone, and MLC20 phosphorylation, partly through the T-855 phosphorylation site of MYPT1.


CONCLUSIONS
Our investigation reveals a hitherto unknown role for αvβ3 integrin as a cerebral arterial pressure sensor. The membrane receptor facilitates Ca(2+) wave generation through a signaling cascade, involving phospholipase Cγ1, inositol 1,3,4 triphosphate production, and inositol 1, 4, 5-triphosphate receptor activation. These discrete asynchronous Ca(2+) events facilitate MLC20 phosphorylation and, in part, myogenic tone by influencing both MLC kinase and MLC phosphatase activity.
From the Hotchkiss Brain Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), Libin Cardiovascular Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), and Department of Physiology and Pharmacology (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), University of Calgary, Alberta, Canada; and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada (A.Z., M.S., N.M., S.E.B., D.G.W.).
Rania E
RE
Mufti
From the Hotchkiss Brain Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), Libin Cardiovascular Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), and Department of Physiology and Pharmacology (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), University of Calgary, Alberta, Canada; and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada (A.Z., M.S., N.M., S.E.B., D.G.W.).
Anil
A
Zechariah
From the Hotchkiss Brain Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), Libin Cardiovascular Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), and Department of Physiology and Pharmacology (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), University of Calgary, Alberta, Canada; and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada (A.Z., M.S., N.M., S.E.B., D.G.W.).
Maria
M
Sancho
From the Hotchkiss Brain Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), Libin Cardiovascular Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), and Department of Physiology and Pharmacology (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), University of Calgary, Alberta, Canada; and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada (A.Z., M.S., N.M., S.E.B., D.G.W.).
Neil
N
Mazumdar
From the Hotchkiss Brain Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), Libin Cardiovascular Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), and Department of Physiology and Pharmacology (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), University of Calgary, Alberta, Canada; and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada (A.Z., M.S., N.M., S.E.B., D.G.W.).
Suzanne E
SE
Brett
From the Hotchkiss Brain Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), Libin Cardiovascular Institute (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), and Department of Physiology and Pharmacology (R.E.M., A.Z., M.S., N.M., S.E.B., D.G.W.), University of Calgary, Alberta, Canada; and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada (A.Z., M.S., N.M., S.E.B., D.G.W.). dwelsh@ucalgary.ca.
Donald G
DG
Welsh
D000818:Animals; D062186:Arterial Pressure; D015153:Blotting, Western; D020013:Calcium Signaling / Q000187:drug effects; D002536:Cerebral Arteries / Q000187:drug effects / Q000378:metabolism*; D002560:Cerebrovascular Circulation / Q000187:drug effects; D005260:Female; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D007295:Inositol Phosphates / Q000378:metabolism; D039302:Integrin alphaVbeta3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D040542:Mechanotransduction, Cellular; D009213:Myography; D018994:Myosin Light Chains / Q000378:metabolism; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism; D043263:Myosin-Light-Chain Phosphatase / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D051966:Phospholipase C gamma / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D054645:Protein Phosphatase 1 / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D012519:Sarcoplasmic Reticulum; D014661:Vasoconstriction / Q000187:drug effects
D053496:Inositol 1,4,5-Trisphosphate Receptors; D007295:Inositol Phosphates; D039302:Integrin alphaVbeta3; D018994:Myosin Light Chains; D009842:Oligopeptides; D010726:Phosphodiesterase Inhibitors; C058161:glycyl-arginyl-glycyl-aspartyl-seryl-proline; C058097:inositol 1,3,4-trisphosphate; D009219:Myosin-Light-Chain Kinase; C499850:Ppp1r12a protein, rat; D054645:Protein Phosphatase 1; D043263:Myosin-Light-Chain Phosphatase; D051966:Phospholipase C gamma
Ca2+ waves; arterial pressure; cerebral arteries; myography; phosphorylation