Cupidin, an isoform of Homer/Vesl, interacts with the actin cytoskeleton and activated rho family small GTPases and is expressed in developing mouse cerebellar granule cells.
A developmentally regulated Homer/Vesl isoform, Cupidin (Homer 2a/Vesl-2Delta11), was isolated from postnatal mouse cerebellum using a fluorescent differential display strategy. The strongest expression of Cupidin was detected in the cerebellar granule cells at approximately postnatal day 7. Cupidin was enriched in the postsynaptic density fraction, and its immunoreactivity was concentrated at glomeruli of the inner granular layer when active synaptogenesis occurred. Cupidin protein could be divided into two functional domains: the N-terminal portion, which was highly conserved among Homer/Vesl family proteins, and the C-terminal portion, which consisted of a putative coiled-coil structure, including several leucine zipper motifs. The N-terminal fragment of Cupidin, which was able to associate with metabotropic glutamate receptor 1 (mGluR1), also interacted with F-actin in vitro. In keeping with this, F-actin immunocytochemically colocalized with Cupidin in cultured cerebellar granule cells, and a Cupidin-mGluR1-actin complex was immunoprecipitated from crude cerebellar lysates using an anti-Cupidin antibody. On the other hand, the C-terminal portion of Cupidin bound to Cdc42, a member of Rho family small GTPases, in a GTP-dependent manner in vitro, and Cupidin functionally interacted with activated-Cdc42 in a heterologous expression system. Together, our findings indicate that Cupidin may serve as a postsynaptic scaffold protein that links mGluR signaling with actin cytoskeleton and Rho family proteins, perhaps during the dynamic phase of morphological changes that occur during synapse formation in cerebellar granule cells.
Shiraishi
Y
Y
Department of Molecular Neurobiology, Institute of Medical Science, The University of Tokyo, Minato-ku, Tokyo 108-8639, Japan.
Mizutani
A
A
Bito
H
H
Fujisawa
K
K
Narumiya
S
S
Mikoshiba
K
K
Furuichi
T
T
D000199:Actins / Q000378:metabolism*; D000375:Aging / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002525:Cerebellar Cortex / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D003001:Cloning, Molecular; D017124:Conserved Sequence; D003599:Cytoskeleton / Q000502:physiology; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D018507:Gene Expression Regulation, Developmental; D000072233:Homer Scaffolding Proteins; D051379:Mice; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D009479:Neuropeptides / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
D000199:Actins; D002352:Carrier Proteins; D020690:GTPase-Activating Proteins; D000072233:Homer Scaffolding Proteins; D009479:Neuropeptides; D011506:Proteins; D018094:Receptors, Metabotropic Glutamate; D011993:Recombinant Fusion Proteins; C104077:metabotropic glutamate receptor type 1; D020558:GTP Phosphohydrolases