CBLC (Cbl proto-oncogene C) functions as an E3 ubiquitin-protein ligase that transfers ubiquitin from E2 enzymes to target proteins for proteasomal degradation. It negatively regulates epidermal growth factor receptor (EGFR) signaling by ubiquitinating activated EGFR and inhibiting MAPK1 activation [UniProt Function]. CBLC also promotes ubiquitination of phosphorylated SRC and modulates RET signaling in collaboration with CD2AP, regulating the rate of RET degradation after ligand activation [UniProt Function]. However, the provided PubMed abstracts do not discuss CBLC proto-oncogene C function. Instead, they extensively address MMACHC (also designated CblC in biochemical literature), a distinct protein involved in vitamin B12 metabolism 1. MMACHC processes dietary cobalamin by removing the upper-axial ligand to generate cob(II)alamin, an essential precursor for two B12-dependent enzymes: cytosolic methionine synthase and mitochondrial methylmalonyl-CoA mutase 1. Mutations in MMACHC cause cblC disease, the most common inborn error of intracellular cobalamin metabolism, characterized by combined homocysteinuria and methylmalonic aciduria 2. Early-onset patients present severe multisystem disease with neurological, ocular, and hematological manifestations, while late-onset patients show milder progressive neurological symptoms 2. Treatment with parenteral hydroxocobalamin significantly improves survival 3. The abstracts provide no information supporting CBLC proto-oncogene C's clinical relevance or disease associations.