Myosin light chain kinase (210 kDa) is a potential cytoskeleton integrator through its unique N-terminal domain.
Recently discovered 210-kDa myosin light chain kinase (MLCK-210) is identical to 108-130 kDa MLCK, the principal regulator of the myosin II molecular motor, except for the presence of a unique amino terminal extension. Our in vitro experiments and transfected cell studies demonstrate that the N-terminal half of MLCK-210 unique tail domain has novel microfilament and microtubule binding activity. Consistent with this activity, the MLCK-210 domain codistributes with microfilaments and microtubules in cultured cells and with soluble tubulin in nocodazole-treated cells. This domain is capable of aggregating tubulin dimers in vitro, causing bundling and branching of microtubules induced by taxol. The N-terminal actin-binding region of MLCK-210 has lower affinity to actin (K(d) = 7.4 microM) than its central D(F/V)RXXL repeat-based actin-binding site and does not protect stress fibers from disassembly triggered by MLCK inhibition in transfected cells. Obtained results suggest that while being resident on microfilaments, MLCK-210 may interact with other cytoskeletal components through its N-terminal domain. Based on available evidence, we propose a model in which MLCK-210 could organize cell motility by simultaneous control of cytoskeleton architecture and actomyosin activation through the novel protein scaffold function of the unique tail domain and the classical MLCK catalytic function of the kinase domain.
Kudryashov
Dmitry S
DS
Russian Cardiology Research Center, Moscow 121552, Russia.
Stepanova
Olga V
OV
Vilitkevich
Elena L
EL
Nikonenko
Tatyana A
TA
Nadezhdina
Elena S
ES
Shanina
Nina A
NA
Lukas
Thomas J
TJ
Van Eldik
Linda J
LJ
Watterson
D Martin
DM
Shirinsky
Vladimir P
VP
D008841:Actin Cytoskeleton / Q000378:metabolism* / Q000648:ultrastructure; D000199:Actins / Q000378:metabolism; D000818:Animals; D001665:Binding Sites / Q000502:physiology; D020134:Catalytic Domain / Q000502:physiology; D002460:Cell Line; D002522:Chlorocebus aethiops; D003599:Cytoskeleton / Q000378:metabolism* / Q000648:ultrastructure; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D008854:Microscopy, Electron; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D008970:Molecular Weight; D024462:Myosin Type II / Q000378:metabolism*; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D011993:Recombinant Fusion Proteins; D022502:Stress Fibers / Q000378:metabolism; D014162:Transfection; D014404:Tubulin / Q000378:metabolism
D000199:Actins; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D014404:Tubulin; D049452:Green Fluorescent Proteins; D009219:Myosin-Light-Chain Kinase; D024462:Myosin Type II