The roles of actin cytoskeleton and microtubules for membrane recycling of a food vacuole in Tetrahymena thermophila

Abstract

Phagocytosis is a fundamental cellular event for the uptake of nutrients from the environment in several kinds of eukaryote. Most ciliates egest waste and undigested materials in food vacuoles (FVs) through a cytoproct, which is a specific organelle for defecation. It is considered that FV egestion is initiated by fusion between the FV membrane and plasma membrane in a cytoproct and completed with retrieval of the membrane into a cytoplasmic space. In addition, electron microscopy indicated that microfilaments might be involved in the recycling process of the FV membrane in ciliates over 30 years ago; however, there is no conclusive evidence. Here we demonstrated actin organization on FV near a cytoproct in Tetrahymena thermophila by using a marker for a cytoproct. Moreover, it was revealed that cells treated with actin cytoskeletal inhibitor, Latrunculin B, might be suppressed for membrane retrieval in a cytoproct following FV egestion. On the other hand, the actin structures, likely to be the site of membrane retrieval, were frequently observed in the cells treated with cytoplasmic microtubules inhibitor, Nocodazole. We concluded that actin filaments were probably required for recycling of the FV membrane in a cytoproct although the role was not essential for FV egestion. In addition, it was possible that microtubules might be involved in transportation of recycling vesicles of FV coated with F-actin.

Ciliates rapidly enhance the frequency of conjugation between Escherichia coli strains through bacterial accumulation in vesicles

“…Latrunculin B, a phagocytosis inhibitor binding to actin and inhibiting microfilament polymerization, is associated with limited bacterial engulfing or vesicle production (Sugita et al, 2009;Zackroff et al, 2002). Cytochalasin D is a weak inhibitor of actin polymerization compared with latrunculin B (Coué et al, 1987).…”

ADF/Cofilin Is Not Essential but Is Critically Important for Actin Activities during Phagocytosis in Tetrahymena thermophila

“…The Tetrahymena actin protein (Act1p) (15) and actin-bundling proteins, including fimbrin (16) and eEF1A (15), all localize near the deep fiber and nascent FVs. Moreover, strong accumulation of actin is seen around the cytoproct (17). Consistently, actin-binding drugs block the formation of FVs in the oral apparatus (18), as well as membrane retrieval after FV ejection in the cytoproct (17).…”

“…Moreover, strong accumulation of actin is seen around the cytoproct (17). Consistently, actin-binding drugs block the formation of FVs in the oral apparatus (18), as well as membrane retrieval after FV ejection in the cytoproct (17). Thus, the actin cytoskeleton may play an important role in the deformation of membranes associated with the formation and ejection of FVs.…”

“…Sugita et al (17) previously showed that the cytoproct-associated "actin clump" is a transient structure engaged in membrane recycling from old FVs; therefore, Adf73p-mediated reorganization of the actin cytoskeleton may be involved in this process.…”

Cerebral ganglion ultrastructure and differential proteins revealed using proteomics in the aplysiid (Notarcus leachii cirrosus Stimpson) under cadmium and lead stress

“…Tubulin forms the cytoskeleton together with actin. The cytoskeleton which is the microtubule and microfilament plays an important role in cell migration, material transportation, cell differentiation and so on (Sugita et al, 2009;Ka et al, 2014;Tavakol et al, 2014). Other than the normal cells, the cytoskeleton is very important to the neurocyte because of the axon and dendrite.…”