文章基本信息

标题：Molecular mechanism of membrane targeting by the GRP1 PH domain
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作者：Ju He ; Rachel M. Haney ; Mohsin Vora 等
期刊名称：JLR Papers In Press
印刷版ISSN：0022-2275
电子版ISSN：1539-7262
出版年度：2008
卷号：49
期号：8
页码：1807-1815
DOI：10.1194/jlr.M800150-JLR200
语种：English
出版社：American Society for Biochemistry and Molecular Biology
摘要：The general receptor for phosphoinositides isoform 1 (GRP1) is recruited to the plasma membrane in response to activation of phosphoinositide 3-kinases and accumulation of phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P₃]. GRP1's pleckstrin homology (PH) domain recognizes PtdIns(3,4,5)P₃ with high specificity and affinity, however, the precise mechanism of its association with membranes remains unclear. Here, we detail the molecular basis of membrane anchoring by the GRP1 PH domain. Our data reveal a multivalent membrane docking involving PtdIns(3,4,5)P₃ binding, regulated by pH and facilitated by electrostatic interactions with other anionic lipids. The specific recognition of PtdIns(3,4,5)P₃ triggers insertion of the GRP1 PH domain into membranes. An acidic environment enhances PtdIns(3,4,5)P₃ binding and increases membrane penetration as demonstrated by NMR and monolayer surface tension and surface plasmon resonance experiments. The GRP1 PH domain displays a 28 nM affinity for POPC/1-palmitoyl-2-oleoyl- sn -glycero-3-phosphoethanolamine/PtdIns(3,4,5)P₃ vesicles at pH 6.0, but binds 22-fold weaker at pH 8.0. The pH sensitivity is attributed in part to the His355 residue, protonation of which is required for the robust interaction with PtdIns(3,4,5)P₃ and significant membrane penetration, as illustrated by mutagenesis data. The binding affinity of the GRP1 PH domain for PtdIns(3,4,5)P₃-containing vesicles is further amplified (by ∼6-fold) by nonspecific electrostatic interactions with phosphatidylserine/phosphatidylinositol. Together, our results provide new insight into the multivalent mechanism of the membrane targeting and regulation of the GRP1 PH domain.