The present invention relates, in general, to an extracellular signal regulated kinase, ERK-5. In particular, the present invention relates to nucleic acid molecules coding for ERK-5; ERK-5 polypeptides; recombinant nucleic acid molecules; cells containing the recombinant nucleic acid molecules; antisense ERK-5 nucleic acid constructs; antibodies having binding affinity to an ERK-5 polypeptide; hybridomes containing the antibodies; nucleic acid probes for the detecting of ERK-5 nucleic acid; a method of detecting ERK-5 nucleic acid or polypeptide in a sample; kits containing nucleic acid probes or antibodies; a method of detecting a compound capable of binding to ERK-5 or a fragment thereof; a method of detecting an agonist or antagonist of ERK-5 activity; a method of agonizing or antagonizing ERK-5 associated activity in a mammal; a method of treating diabetes mellitus, skeletal muscle diseases, Alzheimer's disease, or peripheral neuropathies in a mammal with an agonist or antagonist of ERK-5 activity; and a pharmaceutical composition comprising an ERK-5 agonist or antagonist.