title: Inositol pentakisphosphate isomers bind PH domains with varying specificity and inhibit phosphoinositide interactions.
abstract: BACKGROUND
  PH domains represent one of the most common domains in the human proteome. These domains are recognized as important mediators of protein-phosphoinositide and protein-protein interactions. Phosphoinositides are lipid components of the membrane that function as signaling molecules by targeting proteins to their sites of action. Phosphoinositide based signaling pathways govern a diverse range of important cellular processes including membrane remodeling, differentiation, proliferation and survival. Myo-Inositol phosphates are soluble signaling molecules that are structurally similar to the head groups of phosphoinositides. These molecules have been proposed to function, at least in part, by regulating PH domain-phosphoinositide interactions. Given the structural similarity of inositol phosphates we were interested in examining the specificity of PH domains towards the family of myo-inositol pentakisphosphate isomers.
  
  
  RESULTS
  In work reported here we demonstrate that the C-terminal PH domain of pleckstrin possesses the specificity required to discriminate between different myo-inositol pentakisphosphate isomers. The structural basis for this specificity was determined using high-resolution crystal structures. Moreover, we show that while the PH domain of Grp1 does not possess this high degree of specificity, the PH domain of protein kinase B does.
  
  
  CONCLUSIONS
  These results demonstrate that some PH domains possess enough specificity to discriminate between myo-inositol pentakisphosphate isomers allowing for these molecules to differentially regulate interactions with phosphoinositides. Furthermore, this work contributes to the growing body of evidence supporting myo-inositol phosphates as regulators of important PH domain-phosphoinositide interactions. Finally, in addition to expanding our knowledge of cellular signaling, these results provide a basis for developing tools to probe biological pathways.
authors.affiliation: Department of Biochemistry and Biomedical Sciences, McMaster University, 1200 Main Street West, Hamilton, ON, L8N 3Z5, Canada.
authors.forename: Sean G
authors.initials: SG
authors.lastname: Jackson
authors.forename: Sarra
authors.initials: S
authors.lastname: Al-Saigh
authors.forename: Carsten
authors.initials: C
authors.lastname: Schultz
authors.forename: Murray S
authors.initials: MS
authors.lastname: Junop
mesh_terms: D001665:Binding Sites; D001798:Blood Proteins / Q000737:chemistry* / Q000378:metabolism; D007295:Inositol Phosphates / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000378:metabolism; D007536:Isomerism; D010716:Phosphatidylinositols / Q000378:metabolism*; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D051057:Proto-Oncogene Proteins c-akt / Q000737:chemistry / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry; D015398:Signal Transduction
chemical_list: D001798:Blood Proteins; D007295:Inositol Phosphates; D047908:Intracellular Signaling Peptides and Proteins; D010716:Phosphatidylinositols; D010750:Phosphoproteins; D018160:Receptors, Cytoplasmic and Nuclear; C040985:phosphatidylinositol receptors; C039077:platelet protein P47; C013571:inositol pentaphosphate; D051057:Proto-Oncogene Proteins c-akt