The TRPC2 channel forms protein-protein interactions with Homer and RTP in the rat vomeronasal organ.
BACKGROUND
The signal transduction cascade operational in the vomeronasal organ (VNO) of the olfactory system detects odorants important for prey localization, mating, and social recognition. While the protein machinery transducing these external cues has been individually well characterized, little attention has been paid to the role of protein-protein interactions among these molecules. Development of an in vitro expression system for the transient receptor potential 2 channel (TRPC2), which establishes the first electrical signal in the pheromone transduction pathway, led to the discovery of two protein partners that couple with the channel in the native VNO.


RESULTS
Homer family proteins were expressed in both male and female adult VNO, particularly Homer 1b/c and Homer 3. In addition to this family of scaffolding proteins, the chaperones receptor transporting protein 1 (RTP1) and receptor expression enhancing protein 1 (REEP1) were also expressed. RTP1 was localized broadly across the VNO sensory epithelium, goblet cells, and the soft palate. Both Homer and RTP1 formed protein-protein interactions with TRPC2 in native reciprocal pull-down assays and RTP1 increased surface expression of TRPC2 in in vitro assays. The RTP1-dependent TRPC2 surface expression was paralleled with an increase in ATP-stimulated whole-cell current in an in vitro patch-clamp electrophysiological assay.


CONCLUSIONS
TRPC2 expression and channel activity is regulated by chaperone- and scaffolding-associated proteins, which could modulate the transduction of chemosignals. The developed in vitro expression system, as described here, will be advantageous for detailed investigations into TRPC2 channel activity and cell signalling, for a channel protein that was traditionally difficult to physiologically assess.
Mast
Thomas G
TG
Department of Biological Science, The Florida State University, Tallahassee, FL 32306, USA.
Brann
Jessica H
JH
Fadool
Debra A
DA
D000818:Animals; D000831:Animals, Newborn; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D005260:Female; D000072233:Homer Scaffolding Proteins; D006801:Humans; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism; D008297:Male; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D009831:Olfactory Mucosa / Q000166:cytology / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D054730:Protein Interaction Domains and Motifs / Q000235:genetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000235:genetics*; D012903:Smell / Q000502:physiology; D050052:TRPC Cation Channels / Q000235:genetics / Q000378:metabolism*; D019147:Vomeronasal Organ / Q000166:cytology / Q000378:metabolism*
D002352:Carrier Proteins; C000606614:HOMER1 protein, human; D000072233:Homer Scaffolding Proteins; D007473:Ion Channels; D026901:Membrane Transport Proteins; C495316:RTP1 protein, human; D050052:TRPC Cation Channels; C491857:Trpc2 protein, rat