Herranz et al. report the identification of a fungal arrestin homolog and its role in pH signaling. PalF, a protein containing C-terminal and N-terminal arrestin domains, interacted with PalH, the 7 transmembrane receptor (7TMR) in two-hybrid assays and glutathione-S-transferase (GST) pull-down assays. The N-terminal arrestin domain was responsible for the interaction with the PalH cytoplasmic domain. Growth at alkaline pH was blocked by truncation of the PalH cytoplasmic domain, which disrupted the interaction with PalF. Shifting of mycelia to alkaline pH resulted in decreased mobility of the PalF protein on SDS-PAGE, which was reversed by phosphatase treatment, consistent with pH-dependent phosphorylation of PalF. Ubiquinated forms of PalF were also detected following the shift to alkaline pH. Both phosphorylation and ubiquitination of PalF were abolished in cells deficient for PalH. Thus, as with metazoan arrestin, fungal arrestin appears to contribute to 7TMR signaling, and this signaling involves similar types of posttranslational modifications as those observed for metazoan arrestin.
S. Herranz, J. M. Rodríguez, H.-J. Bussink, J. C. Sánchez-Ferrero, H. N. Arst, Jr., M. A. Peñalva,O. Vincent, Arrestin-related proteins mediate pH signaling in fungi. Proc. Natl. Acad. Sci. U.S.A. 309, 12141-12146 (2005). [Abstract] [Full Text]