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© The Rockefeller University Press,
0021-9525/1998//1961 $5.00
The Journal of Cell Biology, Volume 143, Number 7,
, 1998 1961-1970
Regular Articles |
Nonuniform Microtubular Polarity Established by CHO1/MKLP1 Motor Protein Is Necessary for Process Formation of Podocytes
Department of Cell Biology and Neuroanatomy, University of Minnesota Medical School, Minneapolis, Minnesota 05545; and Department of Medicine and Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461
Podocytes are unique cells that are decisively involved in glomerular filtration. They are equipped with a complex process system consisting of major processes and foot processes whose function is insufficiently understood (Mundel, P., and W. Kriz. 1995. Anat. Embryol. 192:385–397). The major processes of podocytes contain a microtubular cytoskeleton. Taking advantage of a recently established cell culture system for podocytes with preserved ability to form processes (Mundel, P., J. Reiser, A. Zúñiga Mejía Borja, H. Pavenstädt, G.R. Davidson, W. Kriz, and R. Zeller. 1997b. Exp. Cell Res. 36:248–258), we studied the functional significance of the microtubular system in major processes. The following data were obtained: (a) Microtubules (MTs) in podocytes show a nonuniform polarity as revealed by hook-decoration. (b) CHO1/ MKLP1, a kinesin-like motor protein, is associated with MTs in podocytes. (c) Treatment of differentiating podocytes with CHO1/MKLP1 antisense oligonucleotides abolished the formation of processes and the nonuniform polarity of MTs. (d) During the recovery from taxol treatment, taxol-stabilized (nocodazole- resistant) MT fragments were distributed in the cell periphery along newly assembled nocodazole-sensitive MTs. A similar distribution pattern of CHO1/MKLP1 was found under these circumstances, indicating its association with MTs. (e) In the recovery phase after complete depolymerization, MTs reassembled exclusively at centrosomes. Taken together, these findings lead to the conclusion that the nonuniform MT polarity in podocytes established by CHO1/MKLP1 is necessary for process formation.
Key Words: glomerular podocyte • process formation • microtubular polarity • CHO1/MKLP1 • microtubule-organizing center
Abbreviations used in this paper: AF, actin filament; AS, antisense; IF, intermediate filament; MT, microtubule; MTOC, microtubule-organizing center; RT-PCR, reverse transcription PCR; S, sense; TEM, transmission electron microscopy.
The present study was supported by a grant from the Deutsche Forschungsgemeinschaft (DFG) to W. Kriz and P. Mundel. N. Kobayashi was a research fellow of the Alexander von Humboldt Foundation. P. Mundel is a recipient of a "Heisenberg-Stipendium" of the DFG.
Naoto Kobayashi's current address is Department of Anatomy, School of Medicine, University of Ehime, Ehime 791-0295, Japan.
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