Simon Marie Francoise, Rey Astrid, Castan-Laurel Isabelle, Grés Sandra, Sibrac David, Valet Philippe, Saulnier-Blache Jean Sébastien
INSERM U317, Institut Louis Bugnard, Université Paul Sabatier, CHU Rangueil, Batiment L3, 31403, Toulouse cedex 04, France.
J Biol Chem. 2002 Jun 28;277(26):23131-6. doi: 10.1074/jbc.M201530200. Epub 2002 Apr 15.
Because of its production by adipocytes and its ability to increase preadipocyte proliferation, lysophosphatidic acid (LPA) could participate in the paracrine control of adipose tissue development. The aim of the present study was to determine which enzyme activities are involved in exogenous LPA hydrolysis by preadipocytes and adipocytes. Using a quantitative method, we observed that extracellular LPA rapidly disappeared from the culture medium of 3T3F442A preadipocytes. This disappearance was strongly slowed down in the presence of the phosphatase inhibitors, sodium vanadate and sodium pervanadate. By using [(33)P]LPA on intact 3T3F442A preadipocytes, we found that 90% of LPA hydrolysis resulted from LPA phosphatase activity biochemically related to previously described ectolipid phosphate phosphohydrolases (LPPs). Quantitative real time reverse transcriptase-PCR revealed that 3T3F442A preadipocytes expressed mRNAs of three known Lpp gene subtypes (1, 2, and 3), with a predominant expression of Lpp1 and Lpp3. Differentiation of 3T3F442A preadipocytes into adipocytes led to an 80% reduction in ecto-LPA phosphatase activity, with a concomitant down-regulation in Lpp1, Lpp2, and Lpp3 mRNA expression. Despite this regulation, treatment of 3T3F442A adipocytes with sodium vanadate increased LPA production in the culture medium, suggesting the involvement of ecto-LPA phosphatase activity in the control of extracellular production of LPA by adipocytes. In conclusion, these data demonstrate that hydrolysis of extracellular LPA by preadipocytes and adipocytes mainly results from a dephosphorylation activity. This activity (i) occurs at the extracellular face of cell membrane, (ii) exhibits biochemical characteristics similar to those of the LPP, (iii) is negatively regulated during adipocyte differentiation, and (iv) plays an important role in the control of extracellular LPA production by adipocytes. Ecto-LPA phosphatase activity represents a potential target to control adipose tissue development.
由于溶血磷脂酸（LPA）由脂肪细胞产生且具有增加前脂肪细胞增殖的能力，它可能参与脂肪组织发育的旁分泌调控。本研究的目的是确定前脂肪细胞和脂肪细胞对外源LPA水解涉及哪些酶活性。使用定量方法，我们观察到细胞外LPA迅速从3T3F442A前脂肪细胞的培养基中消失。在磷酸酶抑制剂钒酸钠和过钒酸钠存在下，这种消失明显减慢。通过对完整的3T3F442A前脂肪细胞使用[（33）P]LPA，我们发现90%的LPA水解源于与先前描述的胞外脂质磷酸磷酸水解酶（LPPs）生化相关的LPA磷酸酶活性。定量实时逆转录聚合酶链反应显示3T3F442A前脂肪细胞表达三种已知Lpp基因亚型（1、2和3）的mRNA，其中Lpp1和Lpp3表达占主导。3T3F442A前脂肪细胞分化为脂肪细胞导致胞外LPA磷酸酶活性降低80%，同时Lpp1、Lpp2和Lpp3 mRNA表达下调。尽管有这种调控，用钒酸钠处理3T3F442A脂肪细胞会增加培养基中LPA的产生，表明胞外LPA磷酸酶活性参与脂肪细胞对细胞外LPA产生的控制。总之，这些数据表明前脂肪细胞和脂肪细胞对细胞外LPA的水解主要源于去磷酸化活性。这种活性（i）发生在细胞膜的胞外表面，（ii）表现出与LPP相似的生化特征，（iii）在脂肪细胞分化过程中受到负调控，（iv）在脂肪细胞对细胞外LPA产生的控制中起重要作用。胞外LPA磷酸酶活性代表了控制脂肪组织发育的一个潜在靶点。
