title: Properties and functions of TRPM1 channels in the dendritic tips of retinal ON-bipolar cells.
abstract: An increase in light intensity induces a depolarization in retinal ON-bipolar cells via a reduced glutamate release from presynaptic photoreceptor cells. The underlying transduction cascade in the dendritic tips of ON-bipolar cells involves mGluR6 glutamate receptors signaling to TRPM1 proteins that are an indispensable part of the transduction channel. Several other proteins are recognized to participate in the transduction machinery. Deficiency in many of these leads to congenital stationary night blindness, because rod bipolar cells, a subgroup of ON-bipolar cells, constitute the main route for sensory information under scotopic conditions. Here, we review the current knowledge about TRPM1 ion channels and how their activity is regulated within the postsynaptic compartment of ON-bipolar cells. The functional properties of TRPM1 channels in the dendritic compartment are not well understood as they differ substantially from those of recombinant TRPM1 channels. Critical evaluation of possible explanations of these discrepancies indicates that some key components of this transduction pathway might still not be known. The continued exploration of this pathway will yield further clinically useful insights.
authors.affiliation: Institut für Physiologie und Pathophysiologie, Philipps-Universität Marburg, Deutschhausstr. 1-2, D-35037 Marburg, Germany.
authors.forename: Franziska M
authors.initials: FM
authors.lastname: Schneider
authors.affiliation: Institut für Physiologie und Pathophysiologie, Philipps-Universität Marburg, Deutschhausstr. 1-2, D-35037 Marburg, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Mohr
authors.affiliation: Institut für Physiologie und Pathophysiologie, Philipps-Universität Marburg, Deutschhausstr. 1-2, D-35037 Marburg, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Behrendt
authors.affiliation: Institut für Physiologie und Pathophysiologie, Philipps-Universität Marburg, Deutschhausstr. 1-2, D-35037 Marburg, Germany. Electronic address: johannes.oberwinkler@uni-marburg.de.
authors.forename: Johannes
authors.initials: J
authors.lastname: Oberwinkler
mesh_terms: D003712:Dendrites / Q000378:metabolism*; D015785:Eye Diseases, Hereditary / Q000235:genetics / Q000473:pathology; D040181:Genetic Diseases, X-Linked / Q000235:genetics / Q000473:pathology; D006801:Humans; D008027:Light; D009216:Myopia / Q000235:genetics / Q000473:pathology; D009755:Night Blindness / Q000235:genetics / Q000473:pathology; D010786:Photoreceptor Cells / Q000378:metabolism; D017470:Receptors, Glutamate / Q000378:metabolism*; D051245:Retinal Bipolar Cells / Q000166:cytology / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013569:Synapses / Q000502:physiology; D050053:TRPM Cation Channels / Q000378:metabolism*
chemical_list: C576075:GRM6 protein, human; D017470:Receptors, Glutamate; D050053:TRPM Cation Channels; C492059:TRPM1 protein, human
keywords: Congenital stationary night blindness (CSNB); G-protein-coupled signaling; ON-bipolar cells; Retina; Synapse; TRPM1