title: Unique membrane interaction mode of group IIF phospholipase A2.
abstract: The mechanisms by which secretory phospholipases A(2) (PLA(2)s) exert cellular effects are not fully understood. Group IIF PLA(2) (gIIFPLA(2)) is a structurally unique secretory PLA(2) with a long C-terminal extension. Homology modeling suggests that the membrane-binding surface of this acidic PLA(2) contains hydrophobic residues clustered near the C-terminal extension. Vesicle leakage and monolayer penetration measurements showed that gIIFPLA(2) had a unique ability to penetrate and disrupt compactly packed monolayers and bilayers whose lipid composition recapitulates that of the outer plasma membrane of mammalian cells. Fluorescence imaging showed that gIIFPLA(2) could also readily enter and deform plasma membrane-mimicking giant unilamellar vesicles. Mutation analysis indicates that hydrophobic residues (Tyr(115), Phe(116), Val(118), and Tyr(119)) near the C-terminal extension are responsible for these activities. When gIIFPLA(2) was exogenously added to HEK293 cells, it initially bound to the plasma membrane and then rapidly entered the cells in an endocytosis-independent manner, but the cell entry did not lead to a significant degree of phospholipid hydrolysis. GIIFPLA(2) mRNA was detected endogenously in human CD4(+) helper T cells after in vitro stimulation and exogenously added gIIFPLA(2) inhibited the proliferation of a T cell line, which was not seen with group IIA PLA(2). Collectively, these data suggest that unique membrane-binding properties of gIIFPLA(2) may confer special functionality on this secretory PLA(2) under certain physiological conditions.
authors.affiliation: Department of Chemistry (M/C 111), University of Illinois, 845 West Taylor Street, Chicago, IL 60607, USA.
authors.forename: Gihani T
authors.initials: GT
authors.lastname: Wijewickrama
authors.forename: Alexandra
authors.initials: A
authors.lastname: Albanese
authors.forename: Young Jun
authors.initials: YJ
authors.lastname: Kim
authors.forename: Youn Sang
authors.initials: YS
authors.lastname: Oh
authors.forename: Paul S
authors.initials: PS
authors.lastname: Murray
authors.forename: Risa
authors.initials: R
authors.lastname: Takayanagi
authors.forename: Takashi
authors.initials: T
authors.lastname: Tobe
authors.forename: Seiko
authors.initials: S
authors.lastname: Masuda
authors.forename: Makoto
authors.initials: M
authors.lastname: Murakami
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kudo
authors.forename: David S
authors.initials: DS
authors.lastname: Ucker
authors.forename: Diana
authors.initials: D
authors.lastname: Murray
authors.forename: Wonhwa
authors.initials: W
authors.lastname: Cho
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D054501:Group II Phospholipases A2; D006801:Humans; D006825:Hybridomas / Q000187:drug effects; D006868:Hydrolysis; D057927:Hydrophobic and Hydrophilic Interactions; D066298:In Vitro Techniques; D008297:Male; D008563:Membrane Lipids / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010741:Phospholipases A / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D054467:Phospholipases A2; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity; D013379:Substrate Specificity; D013601:T-Lymphocytes / Q000187:drug effects
chemical_list: D008563:Membrane Lipids; D010743:Phospholipids; D012333:RNA, Messenger; D010741:Phospholipases A; D054501:Group II Phospholipases A2; D054467:Phospholipases A2