Zfyve16 regulates the proliferation of B-lymphoid cells

Zfyve16 (a.k.a. endofin or endosome-associated FYVE-domain protein), a member of the FYVE-domain protein family, is involved in endosomal trafficking and in TGF-β, BMP, and EGFR signaling. The FYVE protein SARA regulates the TGF-β signaling pathway by recruiting Smad2/3 and accelerating their phosphorylation, thereby altering their susceptibility to TGF-β-mediated T cell suppression. Zfyve16 binds to Smad4 and their binding affects the formation of Smad2/3-Smad4 complex in TGF-β signaling. However, the in vivo function of Zfyve16 remains unknown. In this study, we generated a Zfyve16 knockout mouse strain (Zfyve16^KO) and examined its hematopoietic phenotypes and hematopoietic reconstruction ability. The proportion of Tcells in the peripheral blood of Zfyve16^KO mice increases compared with that in wild-type mice. This finding is consistent with the role of Zfyve16 in facilitating TGF-β signaling. Unpredictably, B cell proliferation is inhibited in Zfyve16^KO mice. The proliferation potential of Zfyve16^KO B-lymphoid cells also significantly decreases in vitro. These results suggest that Zfyve16 inhibits the proliferation of T cells, possibly through the TGF-β signaling, but upregulates the proliferation of B-lymphoid cells.