title: Compartmentalization of calcium entry pathways in mouse rods.
abstract: Photoreceptor metabolism, gene expression and synaptic transmission take place in a highly polarized structure consisting of the ellipsoid, subellipsoid, cell body and synaptic terminal regions. Although calcium, a key second messenger, regulates cellular functions throughout the photoreceptor, the molecular mechanisms underlying local region-specific action of Ca2+ in photoreceptors are poorly understood. I have investigated the compartmentalization of voltage-dependent and independent Ca2+ channels in mouse photoreceptors. Transient receptor potential channels isoform 6 (TRPC6), a putative store-operated Ca2+ channel, was selectively localized to the cell body of rods. By contrast, voltage-operated Ca2+ channels were expressed in the synaptic terminal and in the ellipsoid/subellipsoid regions. Likewise, Ca2+ store transporters and channels were strongly associated with the subellipsoid region. A moderate TRPC6 signal was observed in cell bodies of bipolar, amacrine and ganglion cells, but was absent from both plexiform layers. These results suggest that Ca2+ entry mechanisms in mammalian photoreceptors and bipolar cells are highly compartmentalized, consistent with local, region-specific activation of Ca2+-dependent processes.
authors.affiliation: Department of Opthalmology, University of San Francisco School of Medicine, San Francisco 94143-0730, USA. krizaj@phy.ucsf.edu
authors.forename: David
authors.initials: D
authors.lastname: Krizaj
mesh_terms: D000818:Animals; D015152:Blotting, Northern / Q000379:methods; D015153:Blotting, Western / Q000379:methods; D064026:Calbindins; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D005455:Fluorescent Antibody Technique / Q000379:methods; D005970:Glutamate Synthase / Q000378:metabolism; D051379:Mice; D019887:Peanut Agglutinin / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D017948:Retinal Rod Photoreceptor Cells / Q000166:cytology / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D015290:Second Messenger Systems / Q000502:physiology; D050052:TRPC Cation Channels / Q000235:genetics / Q000378:metabolism*; D000074287:TRPC6 Cation Channel; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism
chemical_list: D064026:Calbindins; D019887:Peanut Agglutinin; D012333:RNA, Messenger; D019837:Ryanodine Receptor Calcium Release Channel; D064030:S100 Calcium Binding Protein G; D050052:TRPC Cation Channels; D000074287:TRPC6 Cation Channel; C492146:Trpc6 protein, mouse; D050598:Vesicular Glutamate Transport Protein 1; D005970:Glutamate Synthase; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D002118:Calcium