title: Group VIB Ca2+-independent phospholipase A2gamma promotes cellular membrane hydrolysis and prostaglandin production in a manner distinct from other intracellular phospholipases A2.
abstract: Although group VIA Ca2+-independent phospholipase A2beta (iPLA2beta) has been implicated in various cellular events, the functions of other iPLA2 isozymes remain largely elusive. In this study, we examined the cellular functions of group VIB iPLA2gamma. Lentiviral transfection of iPLA2gamma into HEK293 cells resulted in marked increases in spontaneous, stimulus-coupled, and cell death-associated release of arachidonic acid (AA), which was converted to prostaglandin E2 with preferred cyclooxygenase (COX)-1 coupling. Conversely, treatment of HEK293 cells with iPLA2gamma small interfering RNA significantly reduced AA release, indicating the participation of endogenous iPLA2gamma. iPLA2gamma protein appeared in multiple sizes according to cell types, and a 63-kDa form was localized mainly in peroxisomes. Electrospray ionization mass spectrometry of cellular phospholipids revealed that iPLA2gamma and other intracellular PLA2 enzymes acted on different phospholipid subclasses. Transfection of iPLA2gamma into HCA-7 cells also led to increased AA release and prostaglandin E2 synthesis via both COX-1 and COX-2, with a concomitant increase in cell growth. Immunohistochemistry of human colorectal cancer tissues showed elevated expression of iPLA2gamma in adenocarcinoma cells. These results collectively suggest distinct roles for iPLA2beta and iPLA2gamma in cellular homeostasis and signaling, a functional link between peroxisomal AA release and eicosanoid generation, and a potential contribution of iPLA2gamma to tumorigenesis.
authors.affiliation: Department of Health Chemistry, School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan. mako@pharm.showa-u.ac.jp
authors.forename: Makoto
authors.initials: M
authors.lastname: Murakami
authors.forename: Seiko
authors.initials: S
authors.lastname: Masuda
authors.forename: Kaori
authors.initials: K
authors.lastname: Ueda-Semmyo
authors.forename: Emiko
authors.initials: E
authors.lastname: Yoda
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kuwata
authors.forename: Yasukazu
authors.initials: Y
authors.lastname: Takanezawa
authors.forename: Junken
authors.initials: J
authors.lastname: Aoki
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Arai
authors.forename: Hideki
authors.initials: H
authors.lastname: Sumimoto
authors.forename: Yukio
authors.initials: Y
authors.lastname: Ishikawa
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Ishii
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Nakatani
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kudo
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D016923:Cell Death; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D015179:Colorectal Neoplasms / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism; D054522:Group VI Phospholipases A2; D006801:Humans; D006868:Hydrolysis; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D010741:Phospholipases A / Q000235:genetics / Q000378:metabolism*; D054467:Phospholipases A2; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism; D011453:Prostaglandins / Q000096:biosynthesis*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
chemical_list: D005227:Fatty Acids; D007527:Isoenzymes; D010743:Phospholipids; D011453:Prostaglandins; D034741:RNA, Small Interfering; D016718:Arachidonic Acid; D010741:Phospholipases A; D054522:Group VI Phospholipases A2; C516475:PLA2G6 protein, human; D054467:Phospholipases A2; D015232:Dinoprostone