| Co-Investigator(Kenkyū-buntansha) |
KUWATA Hiroshi School of Pharmaceutical Sciences, Assistant, 薬学部, 助手 (80286864)
SHIMBARA Satoko School of Pharmaceutical Sciences, Assistant, 薬学部, 助手 (60266161)
NAKATANI Yoshihito School of Pharmaceutical Sciences, Assistant, 薬学部, 助手 (80266163)
ATSUMI Gen-ichi School of Pharmaceutical Sciences, Assistant, 薬学部, 助手 (70276608)
MURAKAMI Mokoto School of Pharmaceutical Sciences, Assistant Professor, 薬学部, 助教授 (60276607)
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| Budget Amount *help |
¥13,100,000 (Direct Cost: ¥13,100,000)
Fiscal Year 1998: ¥5,500,000 (Direct Cost: ¥5,500,000)
Fiscal Year 1997: ¥7,600,000 (Direct Cost: ¥7,600,000)
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| Research Abstract |
Phospholipase A_2 (PLA_2) represents a growing family of enzymes that catalyze the hydrolysis of phospholipids at the sn-2 position, liberating free fatty acids inducing arachidonic acid (AA), a precursor of bioactive eicosanoids, and lysophospholipids. PLA_2 has been implicated in diverse cellular responses, such as signal transduction, host defense, blood coagulation, cigestion, and membrane remodeling. Accorcing to an updated classification, PLA2_2 can be subdivided into several groups based upon their stnictures and enzymatic characteristics, inducing Ca^2-dependent cytosolic (cPLA_2) and secretory (sPLA_2) PLA_2 isozymes and Ca^<2+>-independent PLA_2 (iPLA_2). In the present study, the functional coupling of several clstinct PLA_2s and two cyclooxygenase (COX) isoforms during immediate and delayed PG-biosynthetic responses was examined cPIA_2, sPLA_2-IIA and sPLA_2-V were " signaling PLA-_2s" that promoted AA release from cells after stimulation with ionophore or bradykinin, which
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evoked the immediate response, and IL-1, which induced the delayed response. AA released by these signaling PLA_2s was converted to PGE_2 by both COXs during the immediate response and pretbminantly by COX-2 during the dulayed response. iPLA,, which plays a crucial role in "phospholipid remodeling', failed to couple with COX-2 during the delayed response, whereas it was linked to ionophore-induced immeciate PGE_2 generation via COX-l in preference to COX-2. sPLA_2-X induced fatty acid release in a manner similar to iPIA_2 rather than other sPLA2s. Extracellular sPLA_2s-IIA and -V.but neither intracellular cPLA_2 nor iPLA_2, augmented PGE_2 synthesis by neighboring COX-expressing cells, implying that these sPLA_2s play a particular role as paracrine amplifiers of the PG-biosynthetic response signal from one cell to another. After cell activation, signaling PLA_2s were localized around the nucleus where both COX isozymes were present. cPLA_2 bound to vimentin, a perinuclear intermeiziate filament protein, in Ca^<2+>-dependent manner and translocated from the cytosol to perinuclear membrane. sPLA_2-IIA bound a GPI-anchored heparan sulfate proteoglycan glypican, which &livered sPLA_2-IIA into caveolae and perinuclear sites and augmented sPLA_2-IIA-meciated A.A release and PGE_2 generation. Less
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