title: alpha-Actinin-dependent cytoskeletal anchorage is important for ICAM-5-mediated neuritic outgrowth.
abstract: Intercellular adhesion molecule-5 (ICAM-5, telencephalin) is a dendrite-expressed membrane glycoprotein of telencephalic neurons in the mammalian brain. By deletion of the cytoplasmic and membrane-spanning domains of ICAM-5, we observed that the membrane distribution of ICAM-5 was determined by the cytoplasmic portion. Therefore we have characterized the intracellular associations of ICAM-5 by using a bacterially expressed glutathione S-transferase (GST) fusion protein encompassing the cytoplasmic part of ICAM-5. One of the main proteins in the neuronal cell line Paju that bound to the ICAM-5 cytodomain was alpha-actinin. ICAM-5 expressed in transfected Paju cells was found in alpha-actinin immunoprecipitates, and ICAM-5 colocalized with alpha-actinin both in Paju cells and in dendritic filopodia and spines of primary hippocampal neurons. We were also able to coprecipitate alpha-actinin from rat brain homogenate. Binding to alpha-actinin appeared to be mediated mainly through the N-terminal region of the ICAM-5 cytodomain, as the ICAM-5(857-861) cytoplasmic peptide (KKGEY) mediated efficient binding to alpha-actinin. Surface plasmon resonance analysis showed that the turnover of the interaction was rapid. In a mutant cell line, Paju-ICAM-5-KK/AA, the distribution was altered, which implies the importance of the lysines in the interaction. Furthermore, we found that the ICAM-5/alpha-actinin interaction is involved in neuritic outgrowth and the ICAM-5(857-861) cytoplasmic peptide induced morphological changes in Paju-ICAM-5 cells. In summary, these results show that the interaction between ICAM-5 and alpha-actinin is mediated through binding of positively charged amino acids near the transmembrane domain of ICAM-5, and this interaction may play an important role in neuronal differentiation.
authors.affiliation: Division of Biochemistry, Faculty of Biosciences, PO Box 56 (Viikinkaari 5), 00014 University of Helsinki, Finland.
authors.forename: Henrietta
authors.initials: H
authors.lastname: Nyman-Huttunen
authors.forename: Li
authors.initials: L
authors.lastname: Tian
authors.forename: Lin
authors.initials: L
authors.lastname: Ning
authors.forename: Carl G
authors.initials: CG
authors.lastname: Gahmberg
mesh_terms: D000185:Actinin / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D048430:Cell Shape; D003599:Cytoskeleton / Q000378:metabolism*; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D016501:Neurites / Q000378:metabolism* / Q000648:ultrastructure; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020349:Surface Plasmon Resonance
chemical_list: D000199:Actins; C504585:Icam5 protein, mouse; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D010455:Peptides; D011993:Recombinant Fusion Proteins; D000185:Actinin