The invention provides isolated nucleic acids molecules, designated GL50 nucleic acid molecules, which encode novel GL50 polypeptides. The invention also provides antisense nucleic acid molecules, recombinant expression vectors containing GL50 nucleic acid molecules, host cells into which the expression vectors have been introduced, and nonhuman transgenic animals in which a GL50 gene has been introduced or disrupted. The invention still further provides isolated GL50 polypeptides, fusion proteins, antigenic peptides and anti-GL50 antibodies. Diagnostic, screening, and therapeutic methods utilizing compositions of the invention are also provided.