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Species Differences in Dopamine Transporters: Postmortem Changes and Glycosylation Differences
Author(s) -
Patel Amrat,
Uhl George,
Kuhar Michael J.
Publication year - 1993
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1993.tb02151.x
Subject(s) - dopamine transporter , glycosylation , transporter , complementary dna , molecular mass , biology , biochemistry , microbiology and biotechnology , molecular cloning , gaba transporter , chemistry , enzyme , gene
The apparent molecular masses of photoaffinity‐labeled dopamine transporters (DATs) from rat, human, dog, and primate kidney COS cells expressing the rat DAT1 cDNA differ. Sequences predicted from cDNA cloning reveal only one amino acid difference between the length of the rat and human DAT but one less site for potential N‐linked glycosylation in the human DAT. Possible posttranslational and postmortem bases for species differences in DAT molecular mass were explored. Rat DAT proteins from striata subjected to ∼5 h of postmortem delay modeled after the human postmortem delay process revealed small but consistent losses in apparent molecular mass and in cocaine analogue binding; the DAT molecular mass displayed no further losses for up to 30 h of model postmortem treatment. Degradative postmortem changes could thus contribute to molecular mass differences between rat and human DATs. Neuraminidase treatment reduced the apparent molecular mass of native rat DAT but not that of the rat DAT expressed in COS cells, suggesting that the sugars added to the DAT expressed in COS cells were different than those added to the rat brain striatal transporter. These differences could account for the somewhat higher K m values for expressed DAT cDNA in COS cells when compared with the wild‐type striatal transporter. These results are in accord with the differences in number of predicted N‐linked glycosylation sites between rat and human DATs and with cell‐type specificity in transporter posttranslational processing.