Acts as an inhibitor of BTK tyrosine kinase activity, thereby playing a role in B-cell development. Down-regulates BTK kinase activity, leading to interference with BTK-mediated calcium mobilization and NF-kappa-B-driven transcription.
Subcellular locations: Cytoplasm, Membrane
Translocates to the plasma membrane upon IgM stimulation.
Subcellular locations: Nucleus
Expressed in DeFew, HEK293T, HeLa and in Jurkat, MC3 and NB4 lymphoid cells (at protein level). Isoform 1 is the predominant isoform expressed in all examined tissues and cell lines. Highly expressed in hemopoietic tissues (fetal liver, spleen, lymph node, thymus, peripheral blood leukocytes and bone marrow). Weakly or not expressed in other tissues.