Nuclear calmodulin-binding proteins in rat neurons.
By using a 125I-calmodulin overlay assay, three major high-affinity calmodulin-binding proteins, showing apparent molecular masses of 135, 60, and 50 kDa, have been detected in purified nuclear fractions isolated from rat neurons. It has been shown that after extraction of the nuclei with nucleases and high salt, all these proteins remain strongly associated with the nuclear matrix. The 60- and 50-kDa proteins have been previously identified as subunits of the calmodulin-dependent protein kinase II. We report here the immunoblot identification of the 135-kDa calmodulin-binding protein as myosin light chain kinase. We also show that the calmodulin-dependent protein phosphatase calcineurin is present in the neuronal nuclei and associated with the nuclear matrix. The nuclear localization of both calcineurin and myosin light chain kinase has been confirmed by immunocytochemical studies.
Departamento de Biología Celular, Universidad de Barcelona, Spain.
M J
MJ
Pujol
R
R
Bosser
M
M
Vendrell
J
J
Serratosa
O
O
Bachs
D000818:Animals; D019703:Calcineurin; D002148:Calmodulin-Binding Proteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D002467:Cell Nucleus / Q000737:chemistry*; D007124:Immunoenzyme Techniques; D008297:Male; D008970:Molecular Weight; D009219:Myosin-Light-Chain Kinase / Q000032:analysis; D009474:Neurons / Q000648:ultrastructure*; D009687:Nuclear Proteins / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000032:analysis; D010766:Phosphorylation; D011494:Protein Kinases / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar
D002148:Calmodulin-Binding Proteins; D009687:Nuclear Proteins; D011494:Protein Kinases; D009219:Myosin-Light-Chain Kinase; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases