Characterisation of the endogenous human peripheral serotonin transporter SLC6A4 reveals surface expression without N-glycosylation

RT-PCR confirmed that human cell lines of diverse peripheral origins express transcripts for the serotonin transporter (sert/slc6a4). Molecular weights reported for the translated protein appear to be quite variable however. Here we compared directly immunoreactive protein generated from cloned sert transfected into HEK293 with that carried endogenously among the cell lines. The dominant glycosylated 85–95 kDa immunoreactive species contained in HEK-sert transfectants was poorly represented in any native cell: instead, discrete 70 and 60 kDa bands were universally detected. Biotinylation of lymphoid cells revealed that the endogenous non-glycosylated 60 kDa but not 70 kDa protein was available at the surface to access exogenous ligands.