Down regulates expression of stem cell growth factor receptor (KIT). Acts as an effector of EpoR (erythropoietin receptor) in controlling KIT expression and may play a central role in erythroid differentiation during the switch between proliferation and maturation (By similarity). Acts as a positive regulator of cell movement while negatively regulating adhesion to stromal cells by inhibiting the ICAM-1-binding activity of beta-2 integrins. Acts as the mediator that relays suppressing signals from the chemokine receptor CXCR4 to beta-2 integrin LFA-1 in hematopoietic precursors. Involved in induction of stress-activated protein kinase (SAPK), but not ERK or p38 MAPK, in response to genotoxic agents. Induces SAPK by a MKK7- and MEKK1-dependent mechanism. The LYN -> MEKK1 -> MKK7 -> SAPK pathway is functional in the induction of apoptosis by genotoxic agents.