Actin filaments and microtubules regulate endocytosis in marginal cells of the stria vascularis.
CONCLUSIONS
Cationized ferritin (CF) was internalized via clathrin-mediated endocytosis. This process depends on clathrin, actin filaments, and microtubules. Microperoxidase (MPO) was internalized via a clathrin- and caveolin-independent endocytic pathway, which was partially dependent on microtubules but independent of clathrin and actin filaments.


OBJECTIVE
We investigated the role of actin filaments and microtubules in the transport of endocytic carrier vesicles (ECVs) from the plasma membrane to the early sorting endosomes, using CF and MPO as tracers.


METHODS
Fifty-five guinea pigs were used. The animals were divided into a CF endocytosis group and an MPO endocytosis group. These groups consisted of control, nocodazole-treated, cytochalasin (Cyt D)-treated, Cyt D + nocodazole-treated, and geldanamycin-treated subgroups.


RESULTS
For CF endocytosis, the following results were obtained. In the nocodazole experiment, in which microtubules were disrupted to form monomeric tubulin, the number of ECVs loaded with CF was greatly decreased. In the Cyt D experiment, in which the actin filaments were disrupted to form monomers, the number of ECVs labeled with CF was also greatly decreased. In the geldanamycin experiment, in which clathrin-mediated endocytosis was regulated and actin stress fibers were dissolved, the endocytosis of CF was severely inhibited. For MPO endocytosis, in the nocodazole experiment, the endocytosis of MPO was markedly suppressed.
Kakigi
Akinobu
A
Department of Otolaryngology, Kochi Medical School, Kochi, Japan. kakigia@med.kochi-u.ac.jp
Okada
Teruhiko
T
Takeda
Taizo
T
Taguchi
Daizo
D
Nishioka
Rie
R
Nishimura
Masahiko
M
D008841:Actin Cytoskeleton / Q000502:physiology*; D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D011992:Endosomes / Q000378:metabolism; D005260:Female; D005293:Ferritins / Q000493:pharmacokinetics; D006168:Guinea Pigs; D008870:Microtubules / Q000502:physiology*; D010544:Peroxidases / Q000493:pharmacokinetics; D013316:Stria Vascularis / Q000166:cytology* / Q000502:physiology
C010297:polycationic ferritin; D005293:Ferritins; D010544:Peroxidases; C021799:microperoxidase