Functional studies of single-site variants in the calmodulin-binding domain of RC3/neurogranin in Xenopus oocytes.
Single-site variants in the calmodulin-binding domain of RC3/neurogranin were heterologously expressed in Xenopus oocytes to examine their effects on serotonin-evoked currents. RC3 variants serine36 -->alanine (Ser36-->Ala), serine36-->glycine (Ser36-->Gly), and phenylalanine37-->tryptophan (Phe37-->Trp), which bind calmodulin but are deficient in protein kinase C (PKC) phosphorylation, display serotonin-evoked Ca(2+)-dependent Cl- currents in oocytes similar to control oocytes. A serine36-->aspartate (Ser36-->Asp) variant, which does not bind calmodulin and mimics the PKC-phosphorylated state of RC3, significantly enhances serotonin-evoked currents in a manner similar to wild-type. The results suggest that RC3 not only regulates the availability of free calmodulin in a dendritic spine but also, when phosphorylated, independently stimulates G-protein coupled second messenger pathways that generate inositol 1,4,5-trisphosphate (IP3), diacylglycerol (DAG) and intracellular Ca2+.
Watson
J B
JB
Mental Retardation Research Center, UCLA School of Medicine 90024-1759, USA. jwatson@npimain.medsch.ucla.edu
Margulies
J E
JE
Coulter
P M
PM
Gerendasy
D D
DD
Sutcliffe
J G
JG
Cohen
R W
RW
D000595:Amino Acid Sequence; D000818:Animals; D002147:Calmodulin / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D002712:Chlorides / Q000502:physiology; D004553:Electric Conductivity; D005260:Female; D014644:Genetic Variation; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism*; D051579:Neurogranin; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D012701:Serotonin / Q000494:pharmacology; D014982:Xenopus laevis
D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D002712:Chlorides; D009419:Nerve Tissue Proteins; D051579:Neurogranin; D012701:Serotonin