Signal-dependent membrane targeting by pleckstrin homology (PH) domains

Abstract

Pleckstrin homology (PH) domains are small protein modules of around 120 amino acids found in many proteins involved in cell signalling, cytoskeletal rearrangement and other processes. Although several different protein ligands have been proposed for PH domains, their only clearly demonstrated physiological function to date is to bind membrane phosphoinositides. The PH domain from phospholipase C-delta(1) binds specifically to PtdIns(4,5)P(2) and its headgroup, and has become a valuable tool for studying cellular PtdIns(4,5)P(2) functions. More recent developments have demonstrated that a subset of PH domains recognizes the products of agonist-stimulated phosphoinositide 3-kinases. Fusion of these PH domains to green fluorescent protein has allowed dramatic demonstrations of their independent ability to drive signal-dependent recruitment of their host proteins to the plasma membrane. We discuss the structural basis for this 3-phosphoinoistide recognition and the role that it plays in cellular signalling. PH domains that bind specifically to phosphoinositides comprise only a minority (perhaps 15%) of those known, raising questions as to the physiological role of the remaining 85% of PH domains. Most (if not all) PH domains bind weakly and non-specifically to phosphoinositides. Studies of dynamin-1 have indicated that oligomerization of its PH domain may be important in driving membrane association. We discuss the possibility that membrane targeting by PH domains with low affinity for phosphoinositides could be driven by alteration of their oligomeric state and thus the avidity of their membrane binding.

The Oxysterol-binding Protein Homologue ORP1L Interacts with Rab7 and Alters Functional Properties of Late Endocytic Compartments

“…The binding properties of ORP1L are thus similar to those of a majority of PHDs studied. Typically, additional interaction determinants or oligomerization of a PHD to increase avidity are necessary for efficient membrane targeting (Lemmon and Ferguson, 2000). The ANK region alone is capable of minimal LE targeting, consistent with the ability of this fragment to interact with Rab7.…”

“…A majority of the known pleckstrin homology domains show affinity for phosphoinositides, and in many cases, these domains function in targeting of proteins to membranes (Lemmon and Ferguson, 2000;Yu et al, 2004). We therefore assayed the interaction of the ORP1L PHD with phosphoinositides using a vesicle pull-down assay in which phosphatidylcholine (PC) vesicles containing 1 mol% of different phosphoinositides were incubated with glutathioneSepharose containing either GST, GST-PHD(ORP1L), or GST-PHD(PLC␦) as a positive control.…”

Determining selectivity of phosphoinositide-binding domains

“…Of the 13 most populous classes of signaling interaction domain found in the human proteome [3], members of more than half have been reported to drive reversible membrane association by such interactions [1,2,4,5]. Domains that have been implicated in head group-specific recognition of phosphoinositides include pleckstrin homology (PH) domains [6,7]; phagocyte oxidase (phox) homology (PX) domains [8]; FYVE domains (for Fab1, YOTB, Vac1 and EEA1) [9]; epsin or AP180 N-terminal homology (ENTH/ANTH) domains [10,11]; and plant homeodomain (PHD) zinc fingers [12]. In addition, phosphoinositide binding has been reported for PDZ (for Postsynaptic density protein, Disc large, Zona occludens) domains [13], FERM (for band Four-point-one, Ezrin, Radixin, Moesin) domains [14], Tubby [15], and MARCKS [16] proteins.…”

Reorganization of Actin Cytoskeleton by the Phosphoinositide Metabolite Glycerophosphoinositol 4-Phosphate

“…Phosphoinositides may act either by directly affecting the function of a variety of proteins involved in specific cellular activities (Toker, 1998;Lemmon and Ferguson, 2000) or as precursors of second messenger molecules via the activity of specific phospholipases (Berridge, 1993;Rhee and Bae, 1997). An example of the former possibility is the formation of molecular complexes where the phosphoinositides behave as specific docking sites at the membrane for proteins containing appropriate recognition domains, such as pleckstrin homology, FYVE (Stenmark and Aasland, 1999;Lemmon and Ferguson, 2000), and Phox homology (Xu et al, 2001) domains. The second case (phosphoinositides acting as precursors of second messengers) is exemplified by the formation of diacylglycerol and of the water-soluble inositol 1,4,5-trisphosphate via hydrolysis of phosphatidylinositol 4,5-bisphosphate by phospholipase C (Berridge, 1993).…”