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