title: Enzymatic properties and regulation of the native isozymes of retinal membrane guanylyl cyclase (RetGC) from mouse photoreceptors.
abstract: Mouse photoreceptor function and survival critically depend on Ca(2+)-regulated retinal membrane guanylyl cyclase (RetGC), comprised of two isozymes, RetGC1 and RetGC2. We characterized the content, catalytic constants, and regulation of native RetGC1 and RetGC2 isozymes using mice lacking guanylyl cyclase activating proteins GCAP1 and GCAP2 and deficient for either GUCY2F or GUCY2E genes, respectively. We found that the characteristics of both native RetGC isozymes were considerably different from other reported estimates made for mammalian RetGCs: the content of RetGC1 per mouse rod outer segments (ROS) was at least 3-fold lower, the molar ratio (RetGC2:RetGC1) 6-fold higher, and the catalytic constants of both GCAP-activated isozymes between 12- and 19-fold higher than previously measured in bovine ROS. The native RetGC isozymes had different basal activity and were accelerated 5-28-fold at physiological concentrations of GCAPs. RetGC2 alone was capable of contributing as much as 135-165 μM cGMP s(-1) or almost 23-28% to the maximal cGMP synthesis rate in mouse ROS. At the maximal level of activation by GCAP, this isozyme alone could provide a significantly high rate of cGMP synthesis compared to what is expected for normal recovery of a mouse rod, and this can help explain some of the unresolved paradoxes of rod physiology. GCAP-activated native RetGC1 and RetGC2 were less sensitive to inhibition by Ca(2+) in the presence of GCAP1 (EC(50Ca) ∼132-139 nM) than GCAP2 (EC(50Ca) ∼50-59 nM), thus arguing that Ca(2+) sensor properties of GCAP in a functional RetGC/GCAP complex are defined not by a particular target isozyme but the intrinsic properties of GCAPs themselves.
authors: Department of Basic Sciences and Pennsylvania College of Optometry, Salus University, Elkins Park, Pennsylvania 19027, USA.
authors: Igor V
authors: IV
authors: Peshenko
authors: Elena V
authors: EV
authors: Olshevskaya
authors: Andrey B
authors: AB
authors: Savchenko
authors: Sukanya
authors: S
authors: Karan
authors: Krzysztof
authors: K
authors: Palczewski
authors: Wolfgang
authors: W
authors: Baehr
authors: Alexander M
authors: AM
authors: Dizhoor
references: Eur J Hum Genet. 2000 Aug;8(8):578-82
references: 10951519
references: Eur J Biochem. 2003 Sep;270(18):3814-21
references: 12950265
references: Photochem Photobiol. 2008 Jul-Aug;84(4):903-10
references: 18346093
references: Nature. 1988 Jul 7;334(6177):64-6
references: 2455233
references: J Biol Chem. 1998 Jul 10;273(28):17311-4
references: 9651312
references: Proc Natl Acad Sci U S A. 1997 Dec 9;94(25):13414-9
references: 9391039
references: Curr Biol. 2008 Dec 23;18(24):1917-21
references: 19084410
references: Eur J Neurosci. 2002 Jan;15(1):63-78
references: 11860507
references: J Neurosci. 2004 Jul 7;24(27):6078-85
references: 15240799
references: Biochemistry. 2009 Feb 10;48(5):850-62
references: 19143494
references: J Biol Chem. 2008 Oct 24;283(43):29135-43
references: 18723510
references: J Neurosci. 1999 Jul 15;19(14):5889-97
references: 10407028
references: Neuron. 1994 Jun;12(6):1345-52
references: 7912093
references: J Biol Chem. 2004 Apr 23;279(17):16903-6
references: 14993224
references: Proc Natl Acad Sci U S A. 2001 Aug 14;98(17):9948-53
references: 11493703
references: J Biol Chem. 1995 Oct 20;270(42):25200-6
references: 7559656
references: Methods Enzymol. 1989;172:230-62
references: 2747529
references: Mol Cell Biochem. 2010 Jan;334(1-2):117-24
references: 19953307
references: J Biol Chem. 2001 Jul 13;276(28):26218-29
references: 11306565
references: Methods. 1999 Dec;19(4):477-84
references: 10581147
references: Biosci Rep. 1997 Oct;17(5):429-73
references: 9419388
references: Proc Natl Acad Sci U S A. 1995 Jun 6;92(12):5535-9
references: 7777544
references: J Neurosci. 2007 Aug 15;27(33):8805-15
references: 17699662
references: Proc Natl Acad Sci U S A. 1998 May 26;95(11):5993-7
references: 9600905
references: Neuron. 1994 Oct;13(4):849-61
references: 7524559
references: J Biol Chem. 2004 Nov 12;279(46):48189-96
references: 15337746
references: J Physiol. 1988 Sep;403:439-71
references: 2473195
references: Mol Cell. 1998 Jul;2(1):129-33
references: 9702199
references: Biochemistry. 1997 Sep 30;36(39):11995-2000
references: 9305994
references: EMBO J. 2002 Apr 2;21(7):1545-54
references: 11927539
references: J Biol Chem. 2007 Jul 27;282(30):21645-52
references: 17545152
references: Am J Hum Genet. 1998 Aug;63(2):651-4
references: 9683616
references: Biochemistry. 2010 Feb 2;49(4):709-17
references: 20050595
references: J Mol Evol. 2004 Aug;59(2):204-217
references: 15486694
references: Biochemistry. 2005 May 17;44(19):7336-45
references: 15882072
references: J Neurochem. 2007 Nov;103(4):1439-46
references: 17868328
references: Pflugers Arch. 2007 Aug;454(5):805-19
references: 17226052
references: Mol Cell Biochem. 1998 Dec;189(1-2):63-70
references: 9879655
references: J Physiol. 2003 Nov 15;553(Pt 1):125-35
references: 14500766
references: Invest Ophthalmol Vis Sci. 2005 Jun;46(6):2156-67
references: 15914637
references: Proc Natl Acad Sci U S A. 1995 Jan 17;92(2):602-6
references: 7831337
references: Biochemistry. 1996 Jul 2;35(26):8478-82
references: 8679607
references: J Biol Chem. 2007 Mar 23;282(12):8837-47
references: 17255100
references: J Neurosci. 1998 Nov 1;18(21):8936-46
references: 9786999
references: J Biol Chem. 1995 Sep 15;270(37):22029-36
references: 7665624
references: Neuron. 2002 Sep 26;36(1):81-91
references: 12367508
references: Biochemistry. 1998 Aug 11;37(32):11264-71
references: 9698373
references: Neuron. 1994 Aug;13(2):395-404
references: 7520254
references: Proc Natl Acad Sci U S A. 2003 May 27;100(11):6783-8
references: 12732716
references: J Biol Chem. 1997 May 23;272(21):13738-42
references: 9153227
references: Biochemistry. 2004 Nov 2;43(43):13796-804
references: 15504042
references: Proc Natl Acad Sci U S A. 2009 Jul 14;106(28):11788-93
references: 19556550
references: J Biol Chem. 2006 Aug 18;281(33):23830-41
references: 16793776
references: J Physiol. 2002 Aug 1;542(Pt 3):843-54
references: 12154183
references: J Gen Physiol. 1985 Jan;85(1):107-21
references: 3968531
references: J Biol Chem. 1997 May 30;272(22):14327-33
references: 9162068
references: J Cell Biol. 2007 Jun 4;177(5):917-25
references: 17535966
references: Proc Natl Acad Sci U S A. 1994 Apr 26;91(9):4014-8
references: 7909609
references: Protein Expr Purif. 1995 Aug;6(4):501-11
references: 8527937
references: J Biol Chem. 1999 Mar 5;274(10):6526-35
references: 10037746