title: Hippocalcin mediates calcium-dependent translocation of brain-type creatine kinase (BB-CK) in hippocampal neurons.
abstract: Hippocalcin (Hpca) is a Ca(2+)-binding protein that is expressed in neurons and contributes to neuronal plasticity. We purified a 48 kDa Hpca-associated protein from rat brain and identified it to be the creatine kinase B (CKB) subunit, which constitutes brain-type creatine kinase (BB-CK). Hpca specifically bound to CKB in a Ca(2+)-dependent manner, but not to the muscle-type creatine kinase M subunit. The N-terminal region of Hpca was required for binding to CKB. Hpca mediated Ca(2+)-dependent partial translocation of CKB (approximately 10-15% of total creatine kinase activity) to membranes. N-myristoylation of Hpca was critical for membrane translocation, but not for binding to CKB. In cultured hippocampal neurons, ionomycin treatment led to colocalization of Hpca and CKB adjacent to the plasma membrane. These results indicate that Hpca associates with BB-CK and that together they translocate to membrane compartments in a Ca(2+)-dependent manner.
authors.affiliation: Department of Physiology, Toho University School of Medicine, Ohmori-nishi 5-21-16, Ohta-ku, Tokyo 143-8540, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Makoto
authors.initials: M
authors.lastname: Hamanoue
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Masaki
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Furuta
authors.forename: Ken
authors.initials: K
authors.lastname: Takamatsu
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D052276:Creatine Kinase, BB Form / Q000378:metabolism*; D051597:Hippocalcin / Q000378:metabolism*; D006624:Hippocampus / Q000201:enzymology*; D051379:Mice; D008817:Mice, Mutant Strains; D021381:Protein Transport; D017966:Pyramidal Cells / Q000201:enzymology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D051597:Hippocalcin; D052276:Creatine Kinase, BB Form; D002118:Calcium