| Literature DB >> 11493703 |
A Mendez1, M E Burns, I Sokal, A M Dizhoor, W Baehr, K Palczewski, D A Baylor, J Chen.
Abstract
The retina's photoreceptor cells adjust their sensitivity to allow photons to be transduced over a wide range of light intensities. One mechanism thought to participate in sensitivity adjustments is Ca(2+) regulation of guanylate cyclase (GC) by guanylate cyclase-activating proteins (GCAPs). We evaluated the contribution of GCAPs to sensitivity regulation in rods by disrupting their expression in transgenic mice. The GC activity from GCAPs-/- retinas showed no Ca(2+) dependence, indicating that Ca(2+) regulation of GCs had indeed been abolished. Flash responses from dark-adapted GCAPs-/- rods were larger and slower than responses from wild-type rods. In addition, the incremental flash sensitivity of GCAPs-/- rods failed to be maintained at wild-type levels in bright steady light. GCAP2 expressed in GCAPs-/- rods restored maximal light-induced GC activity but did not restore normal flash response kinetics. We conclude that GCAPs strongly regulate GC activity in mouse rods, decreasing the flash sensitivity in darkness and increasing the incremental flash sensitivity in bright steady light, thereby extending the rod's operating range.Entities:
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Year: 2001 PMID： 11493703 PMCID： PMC55558 DOI： 10.1073/pnas.171308998
Source DB: PubMed Journal: Proc Natl Acad Sci U S A ISSN： 0027-8424 Impact factor: 11.205