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J. Cell Biol.,
Volume 144, Number 3, February 8, 1999 497-506
Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710
Mitosis in mammalian cells is accompanied
by a dramatic inhibition of endocytosis. We have found
that the addition of amphyphilic compounds to
metaphase cells increases the endocytosis rate even to
interphase levels. Detergents and solvents all increased
endocytosis rate, and the extent of increase was in direct proportion to the concentration added. Although
the compounds could produce a variety of different effects, we have found a strong correlation with a physical
alteration in the membrane tension as measured by the laser tweezers. Plasma membrane tethers formed by latex beads pull back on the beads with a force that was
related to the in-plane bilayer tension and membrane-
cytoskeletal adhesion. We found that as cells enter mitosis, the membrane tension rises as the endocytosis
rate decreases; and as cells exited mitosis, the endocytosis rate increased as the membrane tension decreased. The addition of amphyphilic compounds decreased membrane tension and increased the
endocytosis rate. With the detergent, deoxycholate, the
endocytosis rate was restored to interphase levels when
the membrane tension was restored to interphase levels. Although biochemical factors are clearly involved
in the alterations in mitosis, we suggest that endocytosis
is blocked primarily by the increase in apparent plasma
membrane tension. Higher tensions inhibit both the
binding of the endocytic complex to the membrane and
mechanical deformation of the membrane during invagination. We suggest that membrane tension is an important regulator of the endocytosis rate and alteration
of tension is sufficient to modify endocytosis rates during mitosis. Further, we postulate that the rise in membrane tension causes cell rounding and the inhibition of
motility, characteristic of mitosis.
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