Enables Toll binding activity and interleukin-1 receptor binding activity. Involved in JNK cascade; cell surface receptor signaling pathway; and positive regulation of smooth muscle cell proliferation. Located in postsynaptic density. Part of protein-containing complex. Human ortholog(s) of this gene implicated in Waldenstroem's macroglobulinemia; colorectal carcinoma; and primary immunodeficiency disease. Orthologous to human MYD88 (MYD88 innate immune signal transduction adaptor). [provided by Alliance of Genome Resources, Apr 2022]