Notch Heterodimer NICD Complexes have Divergent Functions Compared to NICD Homodimer Complexes

Abstract

The mammalian Notch signaling system consists of four receptors that can be activated by five membrane bound ligands on adjacent cells. Activation of Notch receptors results in the proteolytic release of Notch intracellular domains (NICD) that translocate to the nucleus to initiate transcriptional programs. Individual N1ICD molecules have been shown to homodimerize on DNA, however a number of basic questions remain regarding dimerization of NICD domains. Based on conserved sequences and structural similarities between NICD domains, we hypothesized that various NICD domains may be able to function as heterodimer complexes and that these heterodimeric complexes may exhibit different transcriptional activities compared to their homodimer counterparts. To address this hypothesis, we devised a co‐immunoprecipitation strategy to examine NICD dimerization in vivo. Our preliminary results show for the first time that some, but not all, NICDs are capable of functioning as heterodimers, even though all NICDs are capable of forming homodimers. This observation, together with the fact that individual cells often express multiple Notch receptors, prompted us to compare the transcriptional activities of homo‐ vs hetero‐dimer complexes. Using a Notch responsive luciferase reporter assay, we determined that NICD heterodimers have transcriptionally divergent activities compared to their NICD homodimer counterparts. Together, these and other observations suggest that signaling in the Notch system does not function solely on a homodimer basis. Instead, and more akin to other signaling systems, our results suggest that Notch signaling will also be influenced by NICD heterodimer complexes.Support or Funding InformationNIH Grant 2R15GM102852‐02This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.