title: Prolonged illumination up-regulates arrestin and two guanylate cyclase activating proteins: a novel mechanism for light adaptation.
abstract: Light adaptation in vertebrate photoreceptors is mediated by multiple mechanisms, one of which could involve nuclear feedback and changes in gene expression. Therefore, we have investigated light adaptation-associated changes in gene expression using microarrays and real-time PCR in isolated photoreceptors, in cultured isolated retinas and in acutely isolated retinas. In all three preparations after 2 h of an exposure to a bright light, we observed an up-regulation of almost 100% of three genes, Sag, Guca1a and Guca1b, coding for proteins known to play a major role in phototransduction: arrestin, GCAP1 and GCAP2. No detectable up-regulation occurred for light exposures of less than 1 h. Functional in vivo electroretinographic tests show that a partial recovery of the dark current occurred 1-2 h after prolonged illumination with a steady light that initially caused a substantial suppression of the photoresponse. These observations demonstrate that prolonged illumination results in the up-regulation of genes coding for proteins involved in the phototransduction signalling cascade, possibly underlying a novel component of light adaptation occurring 1-2 h after the onset of a steady bright light.
authors.affiliation: International School for Advanced Studies (SISSA), Trieste, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Codega
authors.forename: Luca
authors.initials: L
authors.lastname: Della Santina
authors.forename: Claudia
authors.initials: C
authors.lastname: Gargini
authors.forename: Diana E
authors.initials: DE
authors.lastname: Bedolla
authors.forename: Tatiana
authors.initials: T
authors.lastname: Subkhankulova
authors.forename: Frederick J
authors.initials: FJ
authors.lastname: Livesey
authors.forename: Luigi
authors.initials: L
authors.lastname: Cervetto
authors.forename: Vincent
authors.initials: V
authors.lastname: Torre