Unique Membrane Interaction Mode of Group IIF Phospholipase A2

• Published in: The Journal of biological chemistry Vol. 281; no. 43; pp. 32741 - 32754
• Main Authors: Wijewickrama, Gihani T., Albanese, Alexandra, Kim, Young Jun, Oh, Youn Sang, Murray, Paul S., Takayanagi, Risa, Tobe, Takashi, Masuda, Seiko, Murakami, Makoto, Kudo, Ichiro, Ucker, David S., Murray, Diana, Cho, Wonhwa
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 27.10.2006; American Society for Biochemistry and Molecular Biology
• Subjects: Amino Acid Sequence; Animals; Base Sequence; Binding Sites; Cell Division - drug effects; Cell Line; Cell Membrane - chemistry; Cell Membrane - metabolism; Escherichia coli - genetics; Group II Phospholipases A2; Humans; Hybridomas - drug effects; Hydrolysis; Hydrophobic and Hydrophilic Interactions; In Vitro Techniques; Male; Membrane Lipids - chemistry; Membrane Lipids - metabolism; Mice; Models, Molecular; Molecular Sequence Data; Mutation; Phospholipases A - chemistry; Phospholipases A - genetics; Phospholipases A - metabolism; Phospholipases A - pharmacology; Phospholipases A2; Phospholipids - chemistry; Phospholipids - metabolism; RNA, Messenger - metabolism; Sequence Homology, Amino Acid; Static Electricity; Substrate Specificity; T-Lymphocytes - drug effects
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M606311200

The mechanisms by which secretory phospholipases A2 (PLA2s) exert cellular effects are not fully understood. Group IIF PLA2 (gIIFPLA2) is a structurally unique secretory PLA2 with a long C-terminal extension. Homology modeling suggests that the membrane-binding surface of this acidic PLA2 contains hydrophobic residues clustered near the C-terminal extension. Vesicle leakage and monolayer penetration measurements showed that gIIFPLA2 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 gIIFPLA2 could also readily enter and deform plasma membrane-mimicking giant unilamellar vesicles. Mutation analysis indicates that hydrophobic residues (Tyr115, Phe116, Val118, and Tyr119) near the C-terminal extension are responsible for these activities. When gIIFPLA2 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. GIIFPLA2 mRNA was detected endogenously in human CD4+ helper T cells after in vitro stimulation and exogenously added gIIFPLA2 inhibited the proliferation of a T cell line, which was not seen with group IIA PLA2. Collectively, these data suggest that unique membrane-binding properties of gIIFPLA2 may confer special functionality on this secretory PLA2 under certain physiological conditions.