Abstract
The effect of extracellular ATP on adipogenesis was investigated using 3T3-L1 cell line. In this cell line, growth arrest is required before initiation of differentiation, and growth-arrested post-confluent cells can be converted to adipocytes by the presence of the adipogenic hormones. On the other hand, proliferating cells preincubated with ATP for 5 min and subsequently given the adipogenic hormones in the continued presence of 10-100 μM ATP underwent adipocyte differentiation mediated through P2Y receptors, suggesting that extracellular ATP renders preadipocytes responsive to the adipogenic hormones during the growing phase. To determine intracellular proteins playing a role in P2Y receptor-mediated regulation of adipocyte differentiation, we investigated ATP-induced changes in expression profiles of phosphoproteins in 3T3-L1 preadipocytes and found some phosphoproteins modulated by purinergic stimulation. One of the identified phosphoproteins using LC/MS/MS was nucleophosmin. It has been reported that nucleophosmin regulates cell cycle progression and the amount of the phosphorylated form is reduced in growth-arrested state. When the cells were incubated with 100 μM ATP, the expression of phosphorylated nucleophosmin was decreased within 5 min and recovered to the unstimulated level by 30 min incubation. The results suggest the possibility that the modification of nucleophosmin by extracellular ATP induces growth arrest of preadipocytes leading to the proceeding of the differentiation. [J Physiol Sci. 2007;57 Suppl:S125]
