Adapter protein that enhances the efficiency of the MAP kinase cascade. Facilitates the activation of MAPKAPK2 . Heterodimer with MAP2K1IP1. Interacts with ERK and MEK1. Defects in ROBLD3 are the cause of immunodeficiency due to defect in MAPBP-interacting protein. This form of primary immunodeficiency syndrome includes congenital neutropenia, partial albinism, short stature and B-cell and cytotoxic T-cell deficiency. Two alternatively spliced isoforms of the human protein have been described. Note: This description may include information from UniProtKB.