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Proc Natl Acad Sci U S A. 2010 Jan 5;107(1):332-7. doi: 10.1073/pnas.0912730107. Epub 2009 Dec 4.

TRPM1 is a component of the retinal ON bipolar cell transduction channel in the mGluR6 cascade.

Author information

1
Department of Developmental Biology, Osaka Bioscience Institute, Osaka 565-0874, Japan.

Abstract

An essential step in intricate visual processing is the segregation of visual signals into ON and OFF pathways by retinal bipolar cells (BCs). Glutamate released from photoreceptors modulates the photoresponse of ON BCs via metabotropic glutamate receptor 6 (mGluR6) and G protein (Go) that regulates a cation channel. However, the cation channel has not yet been unequivocally identified. Here, we report a mouse TRPM1 long form (TRPM1-L) as the cation channel. We found that TRPM1-L localization is developmentally restricted to the dendritic tips of ON BCs in colocalization with mGluR6. TRPM1 null mutant mice completely lose the photoresponse of ON BCs but not that of OFF BCs. In the TRPM1-L-expressing cells, TRPM1-L functions as a constitutively active nonselective cation channel and its activity is negatively regulated by Go in the mGluR6 cascade. These results demonstrate that TRPM1-L is a component of the ON BC transduction channel downstream of mGluR6 in ON BCs.

PMID:
19966281
PMCID:
PMC2806705
DOI:
10.1073/pnas.0912730107
[Indexed for MEDLINE]
Free PMC Article

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