Regulation of flagellar assembly by glycogen synthase kinase 3 in Chlamydomonas reinhardtii.
Chlamydomonas reinhardtii controls flagellar assembly such that flagella are of an equal and predetermined length. Previous studies demonstrated that lithium, an inhibitor of glycogen synthase kinase 3 (GSK3), induced flagellar elongation, suggesting that a lithium-sensitive signal transduction pathway regulated flagellar length (S. Nakamura, H. Takino, and M. K. Kojima, Cell Struct. Funct. 12:369-374, 1987). Here, we demonstrate that lithium treatment depletes the pool of flagellar proteins from the cell body and that the heterotrimeric kinesin Fla10p accumulates in flagella. We identify GSK3 in Chlamydomonas and demonstrate that its kinase activity is inhibited by lithium in vitro. The tyrosine-phosphorylated, active form of GSK3 was enriched in flagella and GSK3 associated with the axoneme in a phosphorylation-dependent manner. The level of active GSK3 correlated with flagellar length; early during flagellar regeneration, active GSK3 increased over basal levels. This increase in active GSK3 was rapidly lost within 30 min of regeneration as the level of active GSK3 decreased relative to the predeflagellation level. Taken together, these results suggest a possible role for GSK3 in regulating the assembly and length of flagella.
Wilson
Nedra F
NF
Department of Plant Biology, University of Minnesota, 250 Biological Sciences Center, 1445 Gortner Ave., St. Paul, MN 55108, USA. nwilson@biosci.cbs.umn.edu.
Lefebvre
Paul A
PA
D020418:Algal Proteins; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016825:Chlamydomonas reinhardtii / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D003001:Cloning, Molecular; D016054:DNA, Protozoan / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005407:Flagella / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D017125:Genes, Protozoan; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D018021:Lithium Chloride / Q000494:pharmacology; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010641:Phenotype; D010766:Phosphorylation; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014443:Tyrosine / Q000378:metabolism
D020418:Algal Proteins; D016054:DNA, Protozoan; D004791:Enzyme Inhibitors; C088230:KHP1 protein, Chlamydomonas; D008869:Microtubule-Associated Proteins; D015800:Protozoan Proteins; D014443:Tyrosine; D038362:Glycogen Synthase Kinase 3; D018021:Lithium Chloride