title: Lateral diffusion of inositol 1,4,5-trisphosphate receptor type 1 is regulated by actin filaments and 4.1N in neuronal dendrites.
abstract: Inositol 1,4,5-trisphosphate receptor type1 (IP3R1) plays an important role in neuronal functions; however, the lateral diffusion of IP3R1 on the endoplasmic reticulum membrane and its regulation in the living neurons remain unknown. We expressed green fluorescent protein-tagged IP3R1 in cultured rat hippocampal neurons and observed the lateral diffusion by the fluorescence recovery after photobleaching technique. IP3R1 showed lateral diffusion with an effective diffusion constant of approximately 0.3 microm2/s. Depletion of actin filaments increased the diffusion constant of IP3R1, suggesting that the diffusion of IP3R1 is regulated negatively through actin filaments. We also found that protein 4.1N, which binds to IP3R1 and contains an actin-spectrin-binding region, was responsible for this actin regulation of the IP3R1 diffusion constant. Overexpression of dominant-negative 4.1N and blockade of 4.1N binding to IP3R1 increased the IP3R1 diffusion constant. The diffusion of IP3R type 3 (IP3R3), one of the isoforms of IP3Rs lacking the binding ability to 4.1N, was not dependent on actin filaments but became dependent on actin filaments after the addition of a 4.1N-binding sequence. These data suggest that 4.1N serves as a linker protein between IP3R1 and actin filaments. This actin filament-dependent regulation of IP3R1 diffusion may be important for the spatiotemporal regulation of intracellular Ca2+ signaling.
authors.affiliation: Division of Molecular Neurobiology and Division of Neural Signal Information Nippon Telegraph and Telephone Company-The Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
authors.forename: Kazumi
authors.initials: K
authors.lastname: Fukatsu
authors.forename: Hiroko
authors.initials: H
authors.lastname: Bannai
authors.forename: Songbai
authors.initials: S
authors.lastname: Zhang
authors.forename: Hideki
authors.initials: H
authors.lastname: Nakamura
authors.forename: Takafumi
authors.initials: T
authors.lastname: Inoue
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Mikoshiba
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D019556:COS Cells; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000378:metabolism; D003599:Cytoskeleton; D004247:DNA / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D003712:Dendrites / Q000378:metabolism*; D004058:Diffusion; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D005799:Genes, Dominant; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology; D015151:Immunoblotting; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008164:Luminescent Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008954:Models, Biological; D008956:Models, Chemical; D009474:Neurons / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism; D011485:Protein Binding; D020033:Protein Isoforms; D051381:Rats; D017208:Rats, Wistar; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D013997:Time Factors; D000097573:Red Fluorescent Protein
chemical_list: D000199:Actins; D002118:Calcium; D015220:Calcium Channels; D003598:Cytoskeletal Proteins; D004247:DNA; D018076:DNA, Complementary; D049452:Green Fluorescent Proteins; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008164:Luminescent Proteins; D008565:Membrane Proteins; D009479:Neuropeptides; D020033:Protein Isoforms; D018160:Receptors, Cytoplasmic and Nuclear; D000097573:Red Fluorescent Protein; C120557:erythrocyte membrane protein band 4.1-like 1