May be a modulator of the apoptotic response through its ability to affect mitochondrial stability (By similarity). Adapter protein involved in tyrosine kinase and CD28 signaling. Seems to affect CD28-mediated activation of the RE/AP element of the interleukin-2 promoter. Interacts with FES and TNK2. Predominantly expressed in spleen and hematopoietic cells such as peripheral blood leukocytes and weakly expressed in prostate, thymus, heart, small intestine and placenta. May be phosphorylated by FES and ACK1.