Ankrd26 is critical for cell differentiation and cancer-linked mutations affect its key properties

Abstract

Derailed signaling originating from the plasma membrane is associated with many types of cancer. Mutations in ANKRD26 have been linked to different human cancers and to thrombocytopenia. These mutations include an N-terminal truncation associated with acute myeloid leukemia (AML). We conducted an initial characterization of Ankrd26's protein properties and unveil that an N-terminal amphipathic structure of Ankrd26 lacking in the AML-associated mutant is critical for membrane binding and for Ankrd26's ability to bend membranes by partial membrane insertion. Another Ankrd26 mutation linked to papillary thyroid carcinoma includes truncation and fusion with the kinase domain of the protooncogene RET. Our characterization of Ankrd26 properties reveals that the Ankrd26 part in the Ankrd26-RET fusion mutant is able to anchor the RET kinase domain to the plasma membrane and to mediate self-association - a function we demonstrate to be mediated by Ankrd26's coiled coil domain. Ankrd26-RET fusion led to a massive increase in RET autophosphorylation, i.e. to aberrant RET signaling. Understanding the molecular mechanistic properties of Ankrd26 thus provides important insights into Ankrd26-associated pathomechanisms in human cancer patients.