ジアシルグリセロールにより活性化されるTRPC3のB細胞受容体シグナル伝達における生理的意義の解明

抄録

In B lymphocytes, B cell receptor (BCR)-activated Ca²⁺ signaling comprises initial transient responses followed by a Ca²⁺ entry-dependent sustained and/or oscillatory phase. BCR stimulation induces phospholipase C γ2 activation and simulates Ca²⁺ influx across the plasma membrane through multiple mechanisms, such as store-operated Ca²⁺ channels via IP₃-induced Ca²⁺ store depletion and cation/ Ca²⁺ channels directly activated by diacylglycerol (DAG). Previously, we have revealed requirement of store-operated Ca²⁺ channels for the generation of BCR-induced Ca²⁺ oscillations and subsequent gene expression. However, the importance of DAG-activated channels is largely unknown in BCR signalling. Canonical transient receptor potential (TRPC) 3 is known as cation/ Ca²⁺ channels coupled with PLC γ2 and activated by DAG. In this study, we have disrupted TRPC3 gene in DT40 B lymphocytes by targeting method to study its impact on BCR signalling. Endogenous TRPC3 formed DAG-activated Ca²⁺ channels in DT40 B lymphocytes. BCR-induced Ca²⁺ oscillation and NF-AT activation were suppressed in TRPC3-deficient cells. Furthermore, extracellular signal-regulated kinase (ERK), one of the mitogen activated protein kinases (MAPK), activation was reduced in TRPC3-deficient cells. This was attributable to suppressed plasma membrane translocation of PKC βII, a signalling components upstream of the ERK pathway. In conclusion, DAG-dependent activation of TRPC3 plays an important role in BCR-mediated Ca²⁺ and MAPK signalling. [J Physiol Sci. 2006;56 Suppl:S11]