Rab4A GTPase—Catenin Interactions Are Involved in Cell Junction Dynamics in the Testis


Population Council, Center for Biomedical Research, 1230 York Ave, New York, NY 10021 (e-mail: mruk@popcbr.rockefeller.edu).


ABSTRACT: A plethora of evidence has recently accumulated to suggest that Rab guanosine triphosphates (GTPases) may have functions other than those originally proposed in vesicle formation, movement, docking, and fusion. Studies have shown, for example, that Rab proteins interact with actin filaments and microtubules, illustrating cross-talk between intracellular transport and cytoskeletal dynamics. In this report, we show that Rab4A associates with adherens junction signaling proteins in the testis. By immunoprecipitation, Rab4A was found to interact with α- and β-catenin as well as with actin, vimentin, α- and β-tubulin, and protein kinase C (PKC)-α and -ε. Additionally, administration of Adjudin to adult rats up-regulated the Rab4A level, which coincided with the loss of spermatocytes, round and elongating/elongated spermatids from the seminiferous epithelium. More importantly, the ability of Rab4A to associate with α- and β-catenin increased during Adjudin-induced junction restructuring in the testis, illustrating that Rab4A-catenin interactions are likely to be involved in the disassembly of Sertoli—germ cell contacts. Taken collectively, these results suggest that Rab4A participates in adherens junction dynamics.