ISSN 0006-3509, Biophysics, 2010, Vol. 55, No. 6, pp. 916–920. © Pleiades Publishing, Inc., 2010. Original Russian Text © A.V. Burakov, E.S. Nadezhdina, 2010, published in Biofizika, 2010, Vol. 55, No. 6, pp. 996–1001. 916 INTRODUCTION Migration of animal cells, or locomotion, is one of paramount processes, playing a definitive role in development and further vital activity of the multicel- lular organism. During embryo development, orga- nized cell movement in a definite direction takes place already in the course of gastrulation and then during formation of the neural fold and neuraxis. In the adult individual, cell locomotion provides for development of the immune response (cell migration into the inflammatory focus, neutrophil rolling and penetra- tion through the vessel wall). Cell migration takes place during wound healing, in particular, skin injury evokes fibroblast migration into the wound zone; it also happens during remodeling of the blood vessel and myocardium and during development of athero- sclerosis (plaque formation). Cell locomotion plays an important part in carcinogenesis, providing for tumor invasion into surrounding tissue and penetration of single tumor cells into lymph or blood vessels at the stage of metastasis. The main role in cell locomotion belongs to the actomyosin component of the cytoskeleton. However, even the early works devoted to a study of cell motility noted the participation of microtubules in this process [1–3]. Some cells of moderate size, such as fish kera- tocytes or leukocytes, are capable of locomotion at the sole expense of their actomyosin system even after experimental destruction of microtubules [4, 5]. How- ever, the larger fibroblasts after destruction of microtu- bules are capable only of chaotic pseudopodial activity but not of directional movement [1–3]. The role of Editor’s Note: I certify that this text exactly reproduces all factual statements and closely conveys the phrasing and style of the original Russian publication. A.G. microtubules in cell locomotion still remains obscure. It is supposed that microtubules serve as “rails” in the transport of various cell components required for motion to the anterior edge of the cell. The system of dynamic microtubules 25 nm in diameter, consisting of tubulin dimers, in most of animal cells is organized in the form of a radially symmetric star with rays spreading from the cell center to the periphery. Such organization of the tubulin cytoskeleton is optimally adapted for efficient intracellular transport with the aid of motor proteins, specifically binding with various cargoes and directionally transferring them to proper cell compartments. It has been shown that the drop in the rate of migration of a fibroblast is proportional to the decrease in the amount of its microtubules during their gradual disassembly in the presence of nanomo- lar doses of nocodazole [6, 7]. Again, stabilization of microtubules leads to a decrease in cell motility. It has also been shown that microtubules in a moving cell are polarized along the axis of cell movement so that their dynamic plus-ends face the leading edge of the cell, while the centrosome is positioned, as a rule, between the nucleus and the leading edge [8, 9]. This appar- ently determines the direction of membrane transport to the leading edge of the fibroblast, which favors for- mation of new membrane in this place and sets the direction of further cell movement. However, the role of ordered disposition of microtubules also remains obscure. Mammalian fibroblast-like cells owing to their ability of directed locomotion are often used in works devoted to the study of cell motility. Such cells of var- ious lines usually possess a well-organized radially symmetric system of microtubules. The use of chemi- cals to decrease the ability of such cells to move, as a rule, leads either to disassembly of microtubules MOLECULAR BIOPHYSICS Protein Kinase LOSK Regulates the Network of Microtubules and Cell Locomotion A. V. Burakov a and E. S. Nadezhdina b a Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, 119991 Russia b Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142290 Russia Received August 27, 2010 Abstract—It has been found that inhibition of the activity of protein kinase LOSK reduces the ability of cells to perform directed movement over the substrate and changes the parameters of interaction of cells with the substrate. It is suggested that chaotization of microtubules leads to stabilization of cell contacts with the sub- strate and, consequently, to slowdown of locomotion. Keywords: microtubules, locomotion, cell contacts, wound monolayer DOI: 10.1134/S0006350910060059