THE PROTEIN INTERACTOME OF TRANSMEMBRANE PROTEIN 163 (TMEM163)

Abstract

TMEM163 is a currently understudied protein whose function stills requires elucidation. While information on its nature as a zinc influx or efflux transporter is still debated in the literature, this research sought to focus on its relation to the SLC30/ZNT family of zinc transporters. These ZNTs are known to have 10 members, exist as a dimer, efflux zinc, and share functional similarities with TMEM163. Previous research has shown that certain ZNTs form homodimers or heterodimers. This research aims to demonstrate that TMEM163 is a new member of the SLC30/ZNT family and as such, be able to form heterodimeric interaction with related members. More specifically, the goals of this project include characterizing physical interaction of distinct ZNT proteins with TMEM163 and to determine the amino acids or motifs within TMEM163 that are responsible for heterodimerization. Additionally, determination of both colocalization and possible altered sub-cellular localization was carried out to give credence to the interaction having a cellular purpose. Overall, TMEM163 was found to interact with ZNT4 and ZNT8, both members of the SLC30 family, as well as ZIP1, a member of the SLC39 family that influxes zinc into the cytosol. Deletion mutagenesis of TMEM163 did not reveal the potential interaction site within the protein. While the exact amino acids or motif(s) responsible for dimerization remain elusive, it is deemed likely to be located between transmembrane domain 1 to the first half of loop 5. Further, ZNT4, ZNT8, and ZIP1 all partially co-localized with TMEM163 upon heterologous co-expression in cultured HeLa cells. Interestingly, the confocal imaging data shows that TMEM163 co-expression with ZNT4 or ZNT8 altered normal subcellular localizations of both ZNT4 and ZNT8. In conclusion, the results support that TMEM163 is likely a new member of the ZNT family and should be reclassified as ZNT11, and the data provide information for future work on identifying specific amino acids or motifs responsible for protein dimerization