Differential epitope masking reveals synapse-specific complexes of TRPM1

Vis Neurosci. 2018 Jan;35:E001. doi: 10.1017/S0952523817000360.


The transient receptor potential channel TRPM1 is required for synaptic transmission between photoreceptors and the ON subtype of bipolar cells (ON-BPC), mediating depolarization in response to light. TRPM1 is present in the somas and postsynaptic dendritic tips of ON-BPCs. Monoclonal antibodies generated against full-length TRPM1 were found to have differential labeling patterns when used to immunostain the mouse retina, with some yielding reduced labeling of dendritic tips relative to the labeling of cell bodies. Epitope mapping revealed that those antibodies that poorly label the dendritic tips share a binding site (N2d) in the N-terminal arm near the transmembrane domain. A major splice variant of TRPM1 lacking exon 19 does not contain the N2d binding site, but quantitative immunoblotting revealed no enrichment of this variant in synaptsomes. One explanation of the differential labeling is masking of the N2d epitope by formation of a synapse-specific multiprotein complex. Identifying the binding partners that are specific for the fraction of TRPM1 present at the synapses is an ongoing challenge for understanding TRPM1 function.

Keywords: Epitope mapping; Epitope masking; ON bipolar cell; TRPM1.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Monoclonal
  • Blotting, Western
  • Epitope Mapping
  • Epitopes / chemistry*
  • Epitopes / immunology
  • Mice
  • Mice, Inbred C57BL
  • Microscopy, Confocal
  • Polymerase Chain Reaction
  • Protein Isoforms
  • Retinal Bipolar Cells / metabolism*
  • Synapses / physiology*
  • Synaptic Transmission / physiology
  • TRPM Cation Channels / genetics*
  • TRPM Cation Channels / metabolism*


  • Antibodies, Monoclonal
  • Epitopes
  • Protein Isoforms
  • TRPM Cation Channels
  • Trpm1 protein, mouse