Differential localization in cells of myosin II heavy chain kinases during cytokinesis and polarized migration.
BACKGROUND
Cortical myosin-II filaments in Dictyostelium discoideum display enrichment in the posterior of the cell during cell migration, and in the cleavage furrow during cytokinesis. Filament assembly in turn is regulated by phosphorylation in the tail region of the myosin heavy chain (MHC). Early studies have revealed one enzyme, MHCK-A, which participates in filament assembly control, and two other structurally related enzymes, MHCK-B and -C. In this report we evaluate the biochemical properties of MHCK-C, and using fluorescence microscopy in living cells we examine the localization of GFP-labeled MHCK-A, -B, and -C in relation to GFP-myosin-II localization.


RESULTS
Biochemical analysis indicates that MHCK-C can phosphorylate MHC with concomitant disassembly of myosin II filaments. In living cells, GFP-MHCK-A displayed frequent enrichment in the anterior of polarized migrating cells, and in the polar region but not the furrow during cytokinesis. GFP-MHCK-B generally displayed a homogeneous distribution. In migrating cells GFP-MHCK-C displayed posterior enrichment similar to that of myosin II, but did not localize with myosin II to the furrow during the early stage of cytokinesis. At the late stage of cytokinesis, GFP-MHCK-C became strongly enriched in the cleavage furrow, remaining there through completion of division.


CONCLUSIONS
MHCK-A, -B, and -C display distinct cellular localization patterns suggesting different cellular functions and regulation for each MHCK isoform. The strong localization of MHCK-C to the cleavage furrow in the late stages of cell division may reflect a mechanism by which the cell regulates the progressive removal of myosin II as furrowing progresses.
Department of Biochemistry, Stanford University School of Medicine, CA 94305-5307, USA. wliang@cmgm.stamford.edu
Wenchuan
W
Liang
Lucila
L
Licate
Hans
H
Warrick
James
J
Spudich
Thomas
T
Egelhoff
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division / Q000502:physiology; D016764:Cell Polarity / Q000502:physiology*; D004023:Dictyostelium / Q000166:cytology / Q000201:enzymology* / Q000254:growth & development; D049452:Green Fluorescent Proteins; D007399:Interphase / Q000502:physiology; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D024462:Myosin Type II / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection
D007527:Isoenzymes; D008164:Luminescent Proteins; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D000255:Adenosine Triphosphate; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C033142:myosin-heavy-chain kinase; D024462:Myosin Type II; D008274:Magnesium