title: Angiotensin-2-mediated Ca2+ signaling in the retinal pigment epithelium: role of angiotensin-receptor-associated-protein and TRPV2 channel.
abstract: Angiotensin II (AngII) receptor (ATR) is involved in pathologic local events such as neovascularisation and inflammation including in the brain and retina. The retinal pigment epithelium (RPE) expresses ATR in its AT1R form, angiotensin-receptor-associated protein (Atrap), and transient-receptor-potential channel-V2 (TRPV2). AT1R and Atrap co-localize to the basolateral membrane of the RPE, as shown by immunostaining. Stimulation of porcine RPE (pRPE) cells by AngII results in biphasic increases in intracellular free Ca(2+)inhibited by losartan. Xestospongin C (xest C) and U-73122, blockers of IP3R and PLC respectively, reduced AngII-evoked Ca(2+)response. RPE cells from Atrap(-/-) mice showed smaller AngII-evoked Ca(2+)peak (by 22%) and loss of sustained Ca(2+)elevation compared to wild-type. The TRPV channel activator cannabidiol (CBD) at 15 µM stimulates intracellular Ca(2+)-rise suggesting that porcine RPE cells express TRPV2 channels. Further evidence supporting the functional expression of TRPV2 channels comes from experiments in which 100 µM SKF96365 (a TRPV channel inhibitor) reduced the cannabidiol-induced Ca(2+)-rise. Application of SKF96365 or reduction of TRPV2 expression by siRNA reduced the sustained phase of AngII-mediated Ca(2+)transients by 53%. Thus systemic AngII, an effector of the local renin-angiotensin system stimulates biphasic Ca(2+)transients in the RPE by releasing Ca(2+)from cytosolic IP3-dependent stores and activating ATR/Atrap and TRPV2 channels to generate a sustained Ca(2+)elevation.
authors.affiliation: Experimental Ophthalmology, Eye Hospital, University Medical Center Regensburg, Regensburg, Germany.
authors.forename: Rene
authors.initials: R
authors.lastname: Barro-Soria
authors.forename: Julia
authors.initials: J
authors.lastname: Stindl
authors.forename: Claudia
authors.initials: C
authors.lastname: Müller
authors.forename: Renate
authors.initials: R
authors.lastname: Foeckler
authors.forename: Vladimir
authors.initials: V
authors.lastname: Todorov
authors.forename: Hayo
authors.initials: H
authors.lastname: Castrop
authors.forename: Olaf
authors.initials: O
authors.lastname: Strauß
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000804:Angiotensin II / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D004963:Estrenes / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007150:Immunohistochemistry / Q000379:methods; D019808:Losartan / Q000494:pharmacology; D047028:Macrocyclic Compounds / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010080:Oxazoles / Q000378:metabolism; D011760:Pyrrolidinones / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction; D013552:Swine; D050916:TRPV Cation Channels / Q000378:metabolism*
chemical_list: C449676:AGTRAP protein, human; D048868:Adaptor Proteins, Signal Transducing; D004963:Estrenes; D007093:Imidazoles; D047028:Macrocyclic Compounds; D010080:Oxazoles; D011760:Pyrrolidinones; D034741:RNA, Small Interfering; D050916:TRPV Cation Channels; C400769:TRPV2 protein, human; C511704:xestospongin C; D000804:Angiotensin II; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D019808:Losartan; D002118:Calcium