Pleckstrin homology domains: not just for phosphoinositides

Lemmon, Mark

doi:10.1042/bst0320707

Cited by 197 publications

(195 citation statements)

References 36 publications

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“…We propose that SifA antagonizes Rab9 by binding to the SKIP PH domain. PH domains are best known for their binding to phosphoinositides but have been reported to interact with several different types of protein ligands, including a growing list of small G proteins: Arf1, RhoA, Rac1, and Cdc42 (reviewed in 19). Whether the SKIP PH domain:Rab9 interaction occurs in conjunction with phosphoinositides is not known, and the SKIP PH domain is the first shown to be bound to a RabGTPase.…”

Section: Discussionmentioning

confidence: 99%

The Salmonella virulence protein SifA is a G protein antagonist

Jackson

Nawabi

Hentea

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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Salmonella's success at proliferating intracellularly and causing disease depends on the translocation of a major virulence protein, SifA, into the host cell. SifA recruits membranes enriched in lysosome associated membrane protein 1 (LAMP1) and is needed for growth of Salmonella induced filaments (Sifs) and the Salmonella containing vacuole (SCV). It directly binds a host protein called SKIP (SifA and kinesin interacting protein) which is critical for membrane stability and motor dynamics at the SCV. SifA also contains a WxxxE motif, predictive of G protein mimicry in bacterial effectors, but whether and how it mimics the action of a host G protein is not known. We show that SKIP's pleckstrin homology domain, which directly binds SifA, also binds to the late endosomal GTPase Rab9. Knockdown studies suggest that both SKIP and Rab9 function to maintain peripheral LAMP1 distribution in cells. The Rab9:SKIP interaction is GTP-dependent and is inhibited by SifA binding to the SKIP pleckstrin homology domain, suggesting that SifA may be a Rab9 antagonist. SifA:SKIP binding is significantly tighter than Rab9:SKIP binding and may thus allow SifA to bring SKIP to the SCV via SKIP's Rab9-binding site. Rab9 can measurably reverse SifA-dependent LAMP1 recruitment and the perinuclear location of the SCV in cells. Importantly, binding to SKIP requires SifA residues W197 and E201 of the conserved WxxxE signature sequence, leading to the speculation that bacterial G protein mimicry may result in G protein antagonism.GTPase ͉ LAMP1 ͉ Rab9 ͉ SKIP ͉ lysosome

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Section: Discussionmentioning

confidence: 99%

The Salmonella virulence protein SifA is a G protein antagonist

Jackson

Nawabi

Hentea

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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“…This mechanism is analogous to the bridging functions of soluble inositols (28) or to membrane-bound PIP 3 in mediating protein-lipid interactions at the plasma membrane. Candidate binding partners that could dock to this nuclear protein-lipid complex might include the large group of nuclear proteins shown to bind directly to phosphoinositol phosphate head groups (29) or to contain pleckstrin-homology (PH)-domains (30,31). Indeed, the phosphoinositide-dependent kinase-1 (PDK1) PH domain can be docked onto the SF-1/PIP 3 structure and can interface with the PIP 3 head group without any steric clashes at the solvent accessible surfaces (Fig.…”

Section: Discussionmentioning

confidence: 99%

The signaling phospholipid PIP ₃ creates a new interaction surface on the nuclear receptor SF-1

Blind¹,

Sablin

Kuchenbecker

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

129

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The signaling phosphatidylinositol lipids PI(4,5)P 2 (PIP 2 ) and PI (3,4,5)P 3 (PIP 3 ) bind nuclear receptor 5A family (NR5As), but their regulatory mechanisms remain unknown. Here, the crystal structures of human NR5A1 (steroidogenic factor-1, SF-1) ligand binding domain (LBD) bound to PIP 2 and PIP 3 show the lipid hydrophobic tails sequestered in the hormone pocket, as predicted. However, unlike classic nuclear receptor hormones, the phosphoinositide head groups are fully solvent-exposed and complete the LBD fold by organizing the receptor architecture at the hormone pocket entrance. The highest affinity phosphoinositide ligand PIP 3 stabilizes the coactivator binding groove and increases coactivator peptide recruitment. This receptor-ligand topology defines a previously unidentified regulatory protein-lipid surface on SF-1 with the phosphoinositide head group at its nexus and poised to interact with other proteins. This surface on SF-1 coincides with the predicted binding site of the corepressor DAX-1 (dosage-sensitive sex reversal, adrenal hypoplasia critical region on chromosome X), and importantly harbors missense mutations associated with human endocrine disorders. Our data provide the structural basis for this poorly understood cluster of human SF-1 mutations and demonstrates how signaling phosphoinositides function as regulatory ligands for NR5As.T he existence of nuclear, nonmembrane pools of signaling phosphorylated derivatives of phosphatidylinositols or phosphoinositides (PIP n ) was reported over two decades ago (1-3). Consistent with these early reports, lipid-modifying enzymes responsible for phosphoinositide metabolism were also found in the nucleus (4-7); however, the function of PIP n in this cellular compartment remains poorly defined. The nuclear receptors (NRs) steroidogenic factor 1 (SF-1, NR5A1) and liver receptor homolog 1 (LRH-1, NR5A2) bind phosphoinositides as well as other phospholipids in their large hydrophobic pockets (8-13). The ability of NR5As to interact with PIP n is well-conserved with the Caenorhabditis elegans ortholog nhr-25 able to bind both PIP 2 and PIP 3 (14). That phosphoinositides might serve as endogenous NR5A ligands is suggested by the fact that elevating cellular pools of PIP 3 increases SF-1 activity (15) and that impairing PIP 3 uptake decreases SF-1 activity (12). Further, when purified from mammalian cells, the phosphoinositide PIP 2 is found associated with SF-1 and can be modified by the lipid kinase, IPMK, as well as the lipid phosphatase, PTEN (13). Taken together, these data suggest that signaling phosphoinositides are biologically relevant ligands for SF-1.Phosphoinositide ligands diverge chemically from classic NR hormones in that they contain a long, extended hydrophobic moiety and a prominent hydrophilic head group, which is inherently incompatible with the hydrophobic core of the NR5A ligand-binding pocket. Our previous structural analyses of SF-1 bound to phosphatidylcholine suggest that the acyl tails of phosphoinositides should be sequestered...

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“…The PH domain belongs to a structural superfamily that includes the phosphotyrosinebinding, Ena/VASP homology, and Ran-binding domains (27). These domains lack sequence similarity, but all share a core structure of 100 -120 amino acids consisting of a sevenstranded, semi-open, antiparallel ␤-barrel (strands ␤1 to ␤7), capped at one end by a C-terminal ␣-helix (␣1).…”

Section: Sec3nmentioning

confidence: 99%

Structure-Function Study of the N-terminal Domain of Exocyst Subunit Sec3

Baek

Knödler

Lee

et al. 2010

Journal of Biological Chemistry

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The exocyst is an evolutionarily conserved octameric complex involved in polarized exocytosis from yeast to humans. The Sec3 subunit of the exocyst acts as a spatial landmark for exocytosis through its ability to bind phospholipids and small GTPases. The structure of the N-terminal domain of Sec3 (Sec3N) was determined ab initio and defines a new subclass of pleckstrin homology (PH) domains along with a new family of proteins carrying this domain. Respectively, N-and C-terminal to the PH domain Sec3N presents an additional ␣-helix and two ␤-strands that mediate dimerization through domain swapping. The structure identifies residues responsible for phospholipid binding, which when mutated in cells impair the localization of exocyst components at the plasma membrane and lead to defects in exocytosis. Through its ability to bind the small GTPase Cdc42 and phospholipids, the PH domain of Sec3 functions as a coincidence detector at the plasma membrane.The exocyst is an evolutionarily conserved octameric protein complex composed of subunits Sec3, Sec5, Sec6, Sec8, Sec10, Sec15, Exo70, and Exo84. This complex was first identified by genetic and biochemical methods in the budding yeast Saccharomyces cerevisiae (1, 2). A homologous complex was subsequently discovered in mammalian cells (3). The exocyst mediates initial tethering of post-Golgi secretory vesicles to the plasma membrane, a step that precedes SNARE 7 -driven membrane fusion (4, 5). The exocyst is regulated by numerous cellular factors, and in particular small GTPases, which are primarily responsible for the spatiotemporal control of exocytosis (6).Recent studies have provided insights into the molecular architecture and function of tethering proteins. Crystal structures of nearly full-length Exo70 (7-9) and large fragments of Sec6 (10), Sec15 (11), and Exo84 (7) have been determined. Despite the lack of sequence similarity, these structures all reveal a similar fold, consisting of elongated tandem repeats of helical bundles, which are predicted to pack against one another during assembly of the exocyst complex (4). The recently determined structure of the yeast Dsl1p complex implicated in Golgi-to-endoplasmic reticulum transport provided the first glance into an assembled tethering complex consisting of helical bundles similar to those of exocyst subunits (12). The structure suggested a similar architecture, and possibly a common origin, among multisubunit tethering complexes. Structures have also been determined of the RalA-binding domains of the mammalian exocyst subunits Sec5 (13) and Exo84 (14), which display immunoglobulin-like and pleckstrin homology (PH) folds, respectively. However, these two domains are missing in the yeast complex and are not considered part of the conserved core of the exocyst (4).Studies in yeast suggest that subunit Sec3 plays a pivotal role in exocyst function and vesicle tethering. Sec3 localizes, together with Exo70, to the growing end of the daughter cell (known as the "bud tip"). Although the localization of other exocyst c...

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Pleckstrin homology domains: not just for phosphoinositides

Cited by 197 publications

References 36 publications

The Salmonella virulence protein SifA is a G protein antagonist

The Salmonella virulence protein SifA is a G protein antagonist

The signaling phospholipid PIP ₃ creates a new interaction surface on the nuclear receptor SF-1

Structure-Function Study of the N-terminal Domain of Exocyst Subunit Sec3

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Pleckstrin homology domains: not just for phosphoinositides

Cited by 197 publications

References 36 publications

The Salmonella virulence protein SifA is a G protein antagonist

The Salmonella virulence protein SifA is a G protein antagonist

The signaling phospholipid PIP 3 creates a new interaction surface on the nuclear receptor SF-1

Structure-Function Study of the N-terminal Domain of Exocyst Subunit Sec3

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The signaling phospholipid PIP ₃ creates a new interaction surface on the nuclear receptor SF-1