Enables MAP kinase kinase kinase activity. Involved in several processes, including endothelial cell apoptotic process; positive regulation of MAPK cascade; and positive regulation of cardiac muscle cell apoptotic process. Located in cytosol and external side of plasma membrane. Used to study cerebral infarction and myocardial infarction. Biomarker of membranous glomerulonephritis; transient cerebral ischemia; and visual epilepsy. Human ortholog(s) of this gene implicated in Huntington's disease. Orthologous to human MAP3K5 (mitogen-activated protein kinase kinase kinase 5). [provided by Alliance of Genome Resources, Apr 2022]