Novel CARD-3, CARD-4L, CARD-4S, CARD-4Y, CARD-4Z, CARD-5, and CARD-6 polypeptides, proteins, and nucleic acid molecules are disclosed. In addition to isolated CARD-3, CARD-4L, CARD-4S, CARD-4Y, CARD-4Z, CARD-5, and CARD-6 proteins, and the invention further provides CARD-3, CARD-4L, CARD-4S, CARD-4Y, CARD-4Z, CARD-5, and CARD-6 fusion proteins, antigenic peptides and anti-CARD-3, anti-CARD-4L and anti-CARD-4S, anti-CARD-4Y, anti-CARD-4Z, anti-CARD-5, and anti-CARD-6 antibodies. The invention also provides CARD-3, CARD-4L, CARD-4S, CARD-4Y, CARD-4Z, CARD-5, and CARD-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 CARD-3, CARD-4L, CARD-4S, CARD-4Y, CARD-4Z, CARD-5, and CARD-6 gene has been introduced or disrupted. Diagnostic, screening and therapeutic methods utilizing compositions of the invention are also provided.