Abstract
We have investigated possible roles of RhoA and H2O2 in the elevation of intracellular Ca2+ ([Ca2+]i) by phosphatidic acid (PA) in Rat-2 fibroblasts. PA induced a transient elevation of [Ca2+]i in the presence or absence of EGTA. Lysophosphatidic acid (LPA) also increased [Ca2+]i, but the sustained Ca2+ response was inhibited by EGTA. LPA stimulated the production of inositol phosphates, but PA did not. In the presence of EGTA, preincubation with LPA completely blocked the subsequent elevation of [Ca2+]i by PA, but not vice versa. PA stimulated the translocation of RhoA to the particulate fraction as did LPA. Scrape loading of C3 transferase inhibited the transient Ca2+ response to PA, but not to LPA, suggesting an essential role of RhoA in the elevation of [Ca2+]i by PA. H2O2 also induced a transient increase of [Ca2+]i as did PA. H2O2 scavengers, catalase and N-acetyl-L-cysteine, completely blocked the rise of [Ca2+]i stimulated by PA, but not by LPA. Furthermore, preincubation with PA blocked the subsequent Ca2+ response to H2O2, and the incubation with H2O2 also blocked the PA-induced rise of [Ca2+]i. Thus, it was suggested that PA stimulated Ca2+ release from PA-sensitive, but not inositol 1,4,5-trisphosphate-sensitive, Ca2+ stores by the activation of RhoA and intracellular H2O2.
Highlights
The hydrolysis of phosphatidylcholine by phospholipase D produces phosphatidic acid (PA)1 in various cell types stimulated with agonists [1, 2]
PA Increases [Ca2ϩ]i from PA-sensitive Stores—In order to study the mechanism by which PA induces the increase in [Ca2ϩ]i, the level of [Ca2ϩ]i was measured after treating cells with purified PA in Rat-2 fibroblasts
PA Increases [Ca2ϩ]i by RhoA—Since it has been reported that PA stimulated stress fiber formation, which was inhibited by C3 transferase [8], we have investigated the possibility that RhoA was involved in the PA-induced increase of [Ca2ϩ]i
Summary
The hydrolysis of phosphatidylcholine by phospholipase D produces phosphatidic acid (PA) in various cell types stimulated with agonists [1, 2]. It has been reported that PA was involved in the activation of superoxide anion production by activating NADPH oxidase [13,14,15] Another important role of PA in cell signalings is the increase of intracellular Ca2ϩ ([Ca2ϩ]i) [4]. PA has been known to increase [Ca2ϩ]i by the activation of Ca2ϩ efflux from internal stores [4, 17], even though there have been reports suggesting the activation of Ca2ϩ influx by PA [18, 19]. H2O2 scavengers, catalase and N-acetylcysteine (NAC), blocked the PA-induced elevation of [Ca2ϩ]i These observations support the idea that PA increases [Ca2ϩ]i by activating RhoA and the production of intracellular H2O2
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
