PAKa, a putative PAK family member, is required for cytokinesis and the regulation of the cytoskeleton in Dictyostelium discoideum cells during chemotaxis.
We have identified a Dictyostelium discoideum gene encoding a serine/threonine kinase, PAKa, a putative member of the Ste20/PAK family of p21-activated kinases, with a kinase domain and a long NH(2)-terminal regulatory domain containing an acidic segment, a polyproline domain, and a CRIB domain. PAKa colocalizes with myosin II to the cleavage furrow of dividing cells and the posterior of polarized, chemotaxing cells via its NH(2)-terminal domain. paka null cells are defective in completing cytokinesis in suspension. PAKa is also required for maintaining the direction of cell movement, suppressing lateral pseudopod extension, and proper retraction of the posterior of chemotaxing cells. paka null cells are defective in myosin II assembly, as the myosin II cap in the posterior of chemotaxing cells and myosin II assembly into cytoskeleton upon cAMP stimulation are absent in these cells, while constitutively active PAKa leads to an upregulation of myosin II assembly. PAKa kinase activity against histone 2B is transiently stimulated and PAKa incorporates into the cytoskeleton with kinetics similar to those of myosin II assembly in response to chemoattractant signaling. However, PAKa does not phosphorylate myosin II. We suggest that PAKa is a major regulator of myosin II assembly, but does so by negatively regulating myosin II heavy chain kinase.
Chung
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Department of Biology, Center for Molecular Genetics, University of California San Diego, La Jolla, California 92093-0634, USA.
Firtel
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D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D016764:Cell Polarity / Q000187:drug effects; D002633:Chemotaxis / Q000187:drug effects; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism*; D004023:Dictyostelium / Q000166:cytology* / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects; D017353:Gene Deletion; D015726:Giant Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D020930:MAP Kinase Kinase Kinases; D008969:Molecular Sequence Data; D009218:Myosins / Q000235:genetics / Q000378:metabolism*; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011554:Pseudopodia / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D018909:src Homology Domains
D000199:Actins; D047908:Intracellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D000242:Cyclic AMP; C400275:PAKa protein, Dictyostelium discoideum; D017346:Protein Serine-Threonine Kinases; D020930:MAP Kinase Kinase Kinases; C078754:STE20 protein, S cerevisiae; D009218:Myosins