Novel AIP-6 polypeptides, proteins, and nucleic acid molecules are disclosed. In addition to isolated, full-length AIP-6 proteins, the invention further provides isolated AIP-6 fusion proteins, antigenic peptides and anti-AIP-6 antibodies. The invention also provides AIP-6 nucleic acid molecules, recombinant expression vectors containing a nucleic acid molecule of the invention, host cells into which the expression vectors have been introduced and non-human transgenic animals in which a AIP-6 gene has been introduced or disrupted. Diagnostic, screening and therapeutic methods utilizing compositions of the invention are also provided.