SHP-2 modulates interleukin-1-induced Ca2+ flux and ERK activation via phosphorylation of phospholipase Cγ1

Interleukin- 1 ( IL- 1) signaling is dependent on focal adhesions, structures that are enriched with tyrosine kinases and phosphatases. Because the non- receptor tyrosine phosphatase Src homology 2 domain- containing protein tyrosine phosphatase- 2 ( SHP- 2) is enriched in focal adhesions and IL- 1- induced ERK activation requires increased Ca2+, we determined whether SHP- 2 modulates IL- 1- induced Ca2+ signaling. In SHP- 2- deficient fibroblasts, IL- 1- induced Ca2+ signaling and ERK activation were markedly diminished compared with cells expressing SHP- 2. IL- 1- induced Ca2+ release from the endoplasmic reticulum occurred in the vicinity of focal adhesions and was strongly inhibited by the blockage of phospholipase C ( PLC) catalytic activity. Immunoprecipitation and immunostaining showed that SHP- 2, the endoplasmic reticulum- specific protein calnexin, and PLCgamma1 were associated with focal adhesions; however, these associations and IL- 1- induced ERK activation dissipated after cells were plated on non- integrin substrates. IL- 1 promoted phosphorylation of SHP- 2 and PLCgamma1. IL- 1- induced phosphorylation of PLCgamma1 was diminished in SHP- 2- deficient cells but was restored by stable transfection with SHP- 2. BAPTA/ AM ( 1,2- bis( 2aminophenoxy) ethane- N, N, N', N'- tetraacetic acid tetrakis( acetoxymethyl ester)) blocked IL- 1- induced phosphorylation of SHP- 2 and PLCgamma1, indicating mutually dependent interactive roles for Ca2+, SHP- 2, and PLCgamma1 in IL- 1 signaling. We conclude that SHP- 2 is critical for IL- 1- induced phosphorylation of PLCgamma1 and thereby enhances IL- 1- induced Ca2+ release and ERK activation. Focal adhesions co- localizing with the endoplasmic reticulum may provide molecular staging sites required for ERK activation.