title: Localization of guanylate cyclase-activating protein 2 in mammalian retinas.
abstract: Guanylate cyclase-activating proteins (GCAP1 and GCAP2) are thought to mediate the intracellular stimulation of guanylate cyclase (GC) by Ca2+, a key event in recovery of the dark state of rod photoreceptors after exposure to light. GCAP1 has been localized to rod and cone outer segments, the sites of phototransduction, and to photoreceptor synaptic terminals and some cone somata. We used in situ hybridization and immunocytochemistry to localize GCAP2 in human, monkey, and bovine retinas. In human and monkey retinas, the most intense immunolabeling with anti-GCAP2 antibodies was in the cone inner segments, somata, and synaptic terminals and, to a lesser degree, in rod inner segments and inner retinal neurons. In bovine retina, the most intense immunolabeling was in the rod inner segments, with weaker labeling of cone myoids, somata, and synapses. By using a GCAP2-specific antibody in enzymatic assays, we confirmed that GCAP1 but not GCAP2 is the major component that stimulates GC in bovine rod outer segment homogenates. These results suggest that although GCAP1 is involved in the Ca2+-sensitive regulation of GC in rod and cone outer segments, GCAP2 may have non-phototransduction functions in photoreceptors and inner retinal neurons.
authors.affiliation: Department of Ophthalmology, School of Medicine, University of Washington, Seattle, WA 98195, USA.
authors.forename: A
authors.initials: A
authors.lastname: Otto-Bruc
authors.forename: R N
authors.initials: RN
authors.lastname: Fariss
authors.forename: F
authors.initials: F
authors.lastname: Haeseleer
authors.forename: J
authors.initials: J
authors.lastname: Huang
authors.forename: J
authors.initials: J
authors.lastname: Buczyłko
authors.forename: I
authors.initials: I
authors.lastname: Surgucheva
authors.forename: W
authors.initials: W
authors.lastname: Baehr
authors.forename: A H
authors.initials: AH
authors.lastname: Milam
authors.forename: K
authors.initials: K
authors.lastname: Palczewski
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000302:isolation & purification*; D002417:Cattle; D051604:Guanylate Cyclase-Activating Proteins; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008252:Macaca fascicularis; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000302:isolation & purification*; D009474:Neurons / Q000737:chemistry / Q000648:ultrastructure; D010786:Photoreceptor Cells / Q000033:anatomy & histology / Q000737:chemistry*; D012160:Retina / Q000033:anatomy & histology / Q000737:chemistry*; D017949:Retinal Cone Photoreceptor Cells / Q000737:chemistry / Q000648:ultrastructure; D017948:Retinal Rod Photoreceptor Cells / Q000737:chemistry / Q000648:ultrastructure; D013045:Species Specificity; D013569:Synapses / Q000737:chemistry / Q000648:ultrastructure
chemical_list: D002135:Calcium-Binding Proteins; C496736:GUCA1A protein, human; C496739:GUCA1B protein, human; D051604:Guanylate Cyclase-Activating Proteins; D009419:Nerve Tissue Proteins