Characterization of Store-operated Ca2+ Entry in 3T3-L1 Cells

「ABSTRACT」3T3-L1 preadipocytes differentiate into mature adipocytes and are useful for studying the mechanism of obesity. The mobilization of intracellular Ca2+ concentration ([Ca2+]i) is related to adipocyte differentiation. Therefore, we studied the mechanisms regulating [Ca2+]i mobilization in isolated fura-2-loaded 3T3-L1 preadipocytes. Thapsigargin and prostaglandin F2α (PGF2α) are known to cause Ca2+ influx from the extracellular space. However, this influx was inhibited by 2 store-operated Ca2+ entry (SOCE) inhibitors: 2-aminoethoxydiphenyl borate and Ni2+. These results indicated the presence of a SOCE system in 3T3-L1 preadipocytes. Although the actin cytoskeleton plays an important role in many cell functions, whether the actin network affects SOCE remains controversial. Cytochalasin D, an actin-depolymerizing agent, and calyculin A, a cortical actin-reorganizing agent, did not inhibit thapsigargin-induced [Ca2+]i mobilization. These results suggested that the actin cytoskeleton does not participate in SOCE in 3T3-L1 preadipocytes. Canonical transient receptor potential channels (TRPs) have recently been reported to be involved in SOCE. We detected TRPC1 and TRPC2 messenger RNAs by reverse transcriptase polymerase chain reaction. However, we did not observe Sr2+ influx. Therefore, we inferred that TRPCs do not take part in SOCE in 3T3-L1 preadipocytes.