How structural elements evolving from bacterial to human SLC6 transporters enabled new functional properties
Abstract Background Much of the structure-based mechanistic understandings of the function of SLC6A neurotransmitter transporters emerged from the study of their bacterial LeuT-fold homologs. It has become evident, however, that structural differences such as the long N- and C-termini of the eukaryo...
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| Format: | Article |
| Language: | English |
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BMC
2018-03-01
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| Series: | BMC Biology |
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| Online Access: | http://link.springer.com/article/10.1186/s12915-018-0495-6 |
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| author | Asghar M. Razavi George Khelashvili Harel Weinstein |
| author_facet | Asghar M. Razavi George Khelashvili Harel Weinstein |
| author_sort | Asghar M. Razavi |
| collection | DOAJ |
| description | Abstract Background Much of the structure-based mechanistic understandings of the function of SLC6A neurotransmitter transporters emerged from the study of their bacterial LeuT-fold homologs. It has become evident, however, that structural differences such as the long N- and C-termini of the eukaryotic neurotransmitter transporters are involved in an expanded set of functional properties to the eukaryotic transporters. These functional properties are not shared by the bacterial homologs, which lack the structural elements that appeared later in evolution. However, mechanistic insights into some of the measured functional properties of the eukaryotic transporters that have been suggested to involve these structural elements are sparse or merely descriptive. Results To learn how the structural elements added in evolution enable mechanisms of the eukaryotic transporters in ways not shared with their bacterial LeuT-like homologs, we focused on the human dopamine transporter (hDAT) as a prototype. We present the results of a study employing large-scale molecular dynamics simulations and comparative Markov state model analysis of experimentally determined properties of the wild-type and mutant hDAT constructs. These offer a quantitative outline of mechanisms in which a rich spectrum of interactions of the hDAT N-terminus and C-terminus contribute to the regulation of transporter function (e.g., by phosphorylation) and/or to entirely new phenotypes (e.g., reverse uptake (efflux)) that were added in evolution. Conclusions The findings are consistent with the proposal that the size of eukaryotic neurotransmitter transporter termini increased during evolution to enable more functions (e.g., efflux) not shared with the bacterial homologs. The mechanistic explanations for the experimental findings about the modulation of function in DAT, the serotonin transporter, and other eukaryotic transporters reveal separate roles for the distal and proximal segments of the much larger N-terminus in eukaryotic transporters compared to the bacterial ones. The involvement of the proximal and distal segments — such as the role of the proximal segment in sustaining transport in phosphatidylinositol 4,5-bisphosphate-depleted membranes and of the distal segment in modulating efflux — may represent an evolutionary adaptation required for the function of eukaryotic transporters expressed in various cell types of the same organism that differ in the lipid composition and protein complement of their membrane environment. |
| first_indexed | 2024-12-23T14:30:04Z |
| format | Article |
| id | doaj.art-2b821b56ccad4ee3b09d3e0c2f9e8f8d |
| institution | Directory Open Access Journal |
| issn | 1741-7007 |
| language | English |
| last_indexed | 2024-12-23T14:30:04Z |
| publishDate | 2018-03-01 |
| publisher | BMC |
| record_format | Article |
| series | BMC Biology |
| spelling | doaj.art-2b821b56ccad4ee3b09d3e0c2f9e8f8d2022-12-21T17:43:32ZengBMCBMC Biology1741-70072018-03-0116111410.1186/s12915-018-0495-6How structural elements evolving from bacterial to human SLC6 transporters enabled new functional propertiesAsghar M. Razavi0George Khelashvili1Harel Weinstein2Department of Physiology and Biophysics, Weill Cornell Medical College of Cornell UniversityDepartment of Physiology and Biophysics, Weill Cornell Medical College of Cornell UniversityDepartment of Physiology and Biophysics, Weill Cornell Medical College of Cornell UniversityAbstract Background Much of the structure-based mechanistic understandings of the function of SLC6A neurotransmitter transporters emerged from the study of their bacterial LeuT-fold homologs. It has become evident, however, that structural differences such as the long N- and C-termini of the eukaryotic neurotransmitter transporters are involved in an expanded set of functional properties to the eukaryotic transporters. These functional properties are not shared by the bacterial homologs, which lack the structural elements that appeared later in evolution. However, mechanistic insights into some of the measured functional properties of the eukaryotic transporters that have been suggested to involve these structural elements are sparse or merely descriptive. Results To learn how the structural elements added in evolution enable mechanisms of the eukaryotic transporters in ways not shared with their bacterial LeuT-like homologs, we focused on the human dopamine transporter (hDAT) as a prototype. We present the results of a study employing large-scale molecular dynamics simulations and comparative Markov state model analysis of experimentally determined properties of the wild-type and mutant hDAT constructs. These offer a quantitative outline of mechanisms in which a rich spectrum of interactions of the hDAT N-terminus and C-terminus contribute to the regulation of transporter function (e.g., by phosphorylation) and/or to entirely new phenotypes (e.g., reverse uptake (efflux)) that were added in evolution. Conclusions The findings are consistent with the proposal that the size of eukaryotic neurotransmitter transporter termini increased during evolution to enable more functions (e.g., efflux) not shared with the bacterial homologs. The mechanistic explanations for the experimental findings about the modulation of function in DAT, the serotonin transporter, and other eukaryotic transporters reveal separate roles for the distal and proximal segments of the much larger N-terminus in eukaryotic transporters compared to the bacterial ones. The involvement of the proximal and distal segments — such as the role of the proximal segment in sustaining transport in phosphatidylinositol 4,5-bisphosphate-depleted membranes and of the distal segment in modulating efflux — may represent an evolutionary adaptation required for the function of eukaryotic transporters expressed in various cell types of the same organism that differ in the lipid composition and protein complement of their membrane environment.http://link.springer.com/article/10.1186/s12915-018-0495-6Dopamine transportSLC6 neurotransmitter transportersEvolutionary gain of functionMolecular dynamics simulationsMarkov state modelsReverse transport |
| spellingShingle | Asghar M. Razavi George Khelashvili Harel Weinstein How structural elements evolving from bacterial to human SLC6 transporters enabled new functional properties BMC Biology Dopamine transport SLC6 neurotransmitter transporters Evolutionary gain of function Molecular dynamics simulations Markov state models Reverse transport |
| title | How structural elements evolving from bacterial to human SLC6 transporters enabled new functional properties |
| title_full | How structural elements evolving from bacterial to human SLC6 transporters enabled new functional properties |
| title_fullStr | How structural elements evolving from bacterial to human SLC6 transporters enabled new functional properties |
| title_full_unstemmed | How structural elements evolving from bacterial to human SLC6 transporters enabled new functional properties |
| title_short | How structural elements evolving from bacterial to human SLC6 transporters enabled new functional properties |
| title_sort | how structural elements evolving from bacterial to human slc6 transporters enabled new functional properties |
| topic | Dopamine transport SLC6 neurotransmitter transporters Evolutionary gain of function Molecular dynamics simulations Markov state models Reverse transport |
| url | http://link.springer.com/article/10.1186/s12915-018-0495-6 |
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