New light on TRP and TRPL.
Store-operated Ca2+ entry, a mode of Ca2+ influx activated by depletion of Ca2+ from the internal stores, has been detected in a wide variety of cell types and may be the primary mechanism for Ca2+ entry in nonexcitable cells. Nevertheless, until recently, no candidate store-operated channel (SOC) had been identified molecularly. Through the serendipity of Drosophila genetics, a candidate SOC, referred to as Transient Receptor Potential (TRP), has been identified that is essential for the light-induced cation conductance in photoreceptor cells. A combination of in vitro and in vivo studies has provided strong evidence that TRP is a bona fide SOC. Moreover, TRP forms a supramolecular complex, proposed to be critical for feedback regulation and/or activation, that includes rhodopsin, phospholipase C, protein kinase C, calmodulin, and the PDZ domain-containing protein, INAD. INAD seems to be a scaffolding protein that links TRP with several of these other proteins in the complex. TRP also complexes with a related channel subunit, TRP-like, to form a heteromultimer with conductance characteristics distinct from those of TRP or TRP-like homomultimers. A family of proteins related to TRP is conserved from Caenorhabditis elegans to humans, and recent evidence indicates that at least some of these proteins are SOCs. The human TRP-related proteins may mediate many of the store-operated conductances that have been identified previously in a plethora of human cells.
Montell
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Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
D000818:Animals; D017173:Caenorhabditis elegans / Q000502:physiology; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000235:genetics / Q000502:physiology*; D002147:Calmodulin / Q000378:metabolism; D002148:Calmodulin-Binding Proteins / Q000235:genetics / Q000502:physiology*; D017124:Conserved Sequence; D006224:Cricetinae; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000502:physiology; D006801:Humans; D019476:Insect Proteins / Q000235:genetics / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D008954:Models, Biological; D010641:Phenotype; D010716:Phosphatidylinositols / Q000378:metabolism; D010740:Phospholipases / Q000378:metabolism; D010802:Phylogeny; D011493:Protein Kinase C / Q000378:metabolism; D012243:Rhodopsin / Q000378:metabolism; D015398:Signal Transduction; D050051:Transient Receptor Potential Channels; D014785:Vision, Ocular / Q000502:physiology
D015220:Calcium Channels; D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D029721:Drosophila Proteins; D019476:Insect Proteins; D008565:Membrane Proteins; D010716:Phosphatidylinositols; D050051:Transient Receptor Potential Channels; C063169:trp protein, Drosophila; C074192:trpl protein, Drosophila; D012243:Rhodopsin; D011493:Protein Kinase C; D010740:Phospholipases; D002118:Calcium