Swiprosin 1 (SWS1)

Swiprosin-1/EFhd2 (Swip-1) is an EF-hand and coiled-coil–containing adaptor protein with predicted Src homology 3 (SH3). Swip-1 amplifies BCR-induced apoptosis; however, the mechanism of this amplification was unknown. Swip-1 amplified the BCR-induced calcium flux in WEHI231, B62.1, and Bal17 cells. Conversely, the BCR-elicited calcium flux was strongly attenuated in Swip-1–silenced WEHI231 cells, and this was due to a decreased calcium mobilization from intracellular stores. Furthermore, Swip-1 induced the constitutive association of the BCR itself, Syk, and PLCr2 with membrane rafts. Concomitantly, Swip-1 stabilized the association of BCR with tyrosine-phosphorylated proteins, specifically Syk and PLCr2, and enhanced the constitutive interaction of Syk and PLCr2 with Lyn.