The Phox homology (PX) domain, a new player in phosphoinositide signalling

Phosphoinositides are key regulators of diverse cellular processes. The pleckstrin homology (PH) domain mediates the action of Ptdlns(3,4)P-2, Ptdlns(4,5)P-2 and PtdIns(3,4,5)P-3, while the FYVE domain relays the pulse of PtdIns3P. The recent establishment that the Phox homology (PX) domain interacts with PtdIns3P and other phosphoinositides suggests another mechanism by which phosphoinositides can regulate/integrate multiple cellular events via a spectrum of PX domain-containing proteins. Together with the recent discovery that the epsin N-terminal homologue (ENTH) domain interacts with Ptdlns(4,5)P-2, it is becoming clear that phosphoinositides regulate diverse cellular events through interactions with several distinct structural motifs present in many different proteins.