We tested the experimental hypothesis that there would be a significant difference in ErbB4’s proteolysis by TACE that can be attributed to its ALS-related mutations. The mutated variants are both point mutations that each change one of the amino acids in the protein. Such changes may impact the resulting tertiary and quaternary structure of the protein so that any proteolytic enzymes may cut in different places than they normally would. Additionally, the mutations may inhibit or otherwise affect the activity of the TACE enzyme when it binds to the ErbB4 protein, such as through blocking the enzyme's docking site.