CDK-5-mediated neurofilament phosphorylation in SHSY5Y human neuroblastoma cells.
Cyclin-dependent kinase-5 (CDK-5) has been shown to play important roles in neuronal development and neurogenesis. In vitro studies indicate a role of CDK-5 in phosphorylation of neurofilaments (NFs). In this study, we have chosen the human neuroblastoma cell line SHSY5Y as a model system to study the in vivo phosphorylation of NF proteins by CDK-5. Upon differentiation of SHSY5Y cells with retinoic acid, we found that the phosphorylation of high molecular mass (NF-H) and medium molecular mass (NF-M) NFs increased, whereas the CDK-5 protein level and kinase activity were unaffected. The role of CDK-5 in the phosphorylation of cytoskeletal proteins was studied by using antisense oligonucleotides (ONs) to inhibit the expression of the CDK-5 gene. We found that inhibition of CDK-5 levels by antisense ON treatment resulted in a decrease in phosphorylation of NF-H that correlated with a decline in neurite outgrowth. These results demonstrate that CDK-5 is a major proline-directed kinase phosphorylating the human NF-H tail domain.
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Laboratory of Neurochemistry, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
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D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D018613:Microscopy, Confocal; D008970:Molecular Weight; D009447:Neuroblastoma / Q000201:enzymology* / Q000473:pathology; D016900:Neurofilament Proteins / Q000378:metabolism*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010750:Phosphoproteins / Q000032:analysis; D010766:Phosphorylation; D014212:Tretinoin / Q000494:pharmacology
D007527:Isoenzymes; D016900:Neurofilament Proteins; D016376:Oligonucleotides, Antisense; D010750:Phosphoproteins; C051774:neurofilament protein H; D014212:Tretinoin; D018844:Cyclin-Dependent Kinases