[Possible involvement of Ankhzn, a novel protein possessing FYVE domain, in cellular endocytosis and autophagocytosis in vitro].

The objective of this study was to investigate the functional significance of Ankhzn, a novel zinc binding FYVE finger protein, which was previously identified by our gene trap experiment. On the basis of the fact that a family of FYVE double zinc finger proteins is involved in membrane transport, the present immunohistochemical study was undertaken with a focus on the localization of Ankhzn and endocytotic structures. First, the distribution of Ankhzn was observed in mouse macrophages that were in the process of incorporation of dextran particles in vitro. Ankhzn was further demonstrated in phagocytosed transferrin labeled with Texas red. Second, the topological relationship between the localization of Ankhzn and that of transferrin receptor was studied in neuroblastoma-derived B103 cells. Some but not all Ankhzn immunoreactive vesicles simultaneously contained transferrin receptor. Third, the immunoreactivity of Ankhzn was compared between serum-supplemented and serum-free cultures of B103 cells. A marked increase in the immunostaining of Ankhzn was seen in starved B103 cells. All of these observations suggest that Ankhzn is essential for the formation of endocytotic and autophagocytotic vesicles.

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