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Castagna M, Cinquetti R, Verri T, Vacca F, Giovanola M, Barca A, Romanazzi T, Roseti C, Galli A, Bossi E. The Lepidopteran KAAT1 and CAATCH1: Orthologs to Understand Structure-Function Relationships in Mammalian SLC6 Transporters. Neurochem Res 2021; 47:111-126. [PMID: 34304372 PMCID: PMC8310414 DOI: 10.1007/s11064-021-03410-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2021] [Revised: 04/18/2021] [Accepted: 07/20/2021] [Indexed: 11/16/2022]
Abstract
To the SLC6 family belong 20 human transporters that utilize the sodium electrochemical gradient to move biogenic amines, osmolytes, amino acids and related compounds into cells. They are classified into two functional groups, the Neurotransmitter transporters (NTT) and Nutrient amino acid transporters (NAT). Here we summarize how since their first cloning in 1998, the insect (Lepidopteran) Orthologs of the SLC6 family transporters have represented very important tools for investigating functional–structural relationships, mechanism of transport, ion and pH dependence and substate interaction of the mammalian (and human) counterparts.
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Affiliation(s)
- Michela Castagna
- Department of Pharmacological and Biomolecular Sciences, Università degli Studi di Milano, Via Trentacoste 2, 20134, Milan, Italy
| | - Raffaella Cinquetti
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, via Dunant 3, 21100, Varese, Italy
| | - Tiziano Verri
- Laboratory of Applied Physiology, Department of Biological and Environmental Sciences and Technologies, University of Salento, Via Provinciale Lecce-Monteroni, 73100, Lecce, Italy
| | - Francesca Vacca
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, via Dunant 3, 21100, Varese, Italy
| | - Matteo Giovanola
- Department of Pharmacological and Biomolecular Sciences, Università degli Studi di Milano, Via Trentacoste 2, 20134, Milan, Italy
| | - Amilcare Barca
- Laboratory of Applied Physiology, Department of Biological and Environmental Sciences and Technologies, University of Salento, Via Provinciale Lecce-Monteroni, 73100, Lecce, Italy
| | - Tiziana Romanazzi
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, via Dunant 3, 21100, Varese, Italy
| | - Cristina Roseti
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, via Dunant 3, 21100, Varese, Italy.,Research Centre for Neuroscience, University of Insubria, Varese, Italy
| | - Alessandra Galli
- Department of Pharmacological and Biomolecular Sciences, Università degli Studi di Milano, Via Trentacoste 2, 20134, Milan, Italy
| | - Elena Bossi
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, via Dunant 3, 21100, Varese, Italy. .,Research Centre for Neuroscience, University of Insubria, Varese, Italy.
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Giovanola M, Vollero A, Cinquetti R, Bossi E, Forrest LR, Di Cairano ES, Castagna M. Threonine 67 is a key component in the coupling of the NSS amino acid transporter KAAT1. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:1179-1186. [PMID: 29409909 DOI: 10.1016/j.bbamem.2018.01.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 01/26/2018] [Accepted: 01/28/2018] [Indexed: 01/30/2023]
Affiliation(s)
- M Giovanola
- Department of Pharmacological and Biomolecular Sciences, Università degli Studi di Milano, Via Trentacoste 2, 20134, Milano, Italy
| | - A Vollero
- Department of Biotechnology and Life Sciences, University of Insubria, Via J.H. Dunant 3, 21100, Varese, Italy
| | - R Cinquetti
- Department of Biotechnology and Life Sciences, University of Insubria, Via J.H. Dunant 3, 21100, Varese, Italy
| | - E Bossi
- Department of Biotechnology and Life Sciences, University of Insubria, Via J.H. Dunant 3, 21100, Varese, Italy
| | - L R Forrest
- Computational Structural Biology Section, NIH NINDS, 35 Convent Drive, Bethesda, MD 20892-3761, USA
| | - E S Di Cairano
- Department of Pharmacological and Biomolecular Sciences, Università degli Studi di Milano, Via Trentacoste 2, 20134, Milano, Italy
| | - M Castagna
- Department of Pharmacological and Biomolecular Sciences, Università degli Studi di Milano, Via Trentacoste 2, 20134, Milano, Italy.
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Giovanola M, D'Antoni F, Santacroce M, Mari SA, Cherubino F, Bossi E, Sacchi VF, Castagna M. Role of a conserved glycine triplet in the NSS amino acid transporter KAAT1. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1818:1737-44. [PMID: 22402268 DOI: 10.1016/j.bbamem.2012.02.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Revised: 02/15/2012] [Accepted: 02/20/2012] [Indexed: 10/28/2022]
Abstract
K+-coupled amino acid transporter 1 (KAAT1) belongs to the NSS family of solute transporters and it is expressed in the midgut and in salivary glands of Manduca sexta larvae. As more than 80% of family members, KAATI shows a stretch of three glycines (G85-G87) that according to the structure of the prototype transporter LeuT, is located close to the access of the permeation pathway. In this work the role of the triplet has been investigated by alanine and cysteine scanning methods in protein heterologously expressed in Xenopus laevis oocytes. All the mutants were functional but the surface expression level was reduced for G85A and G87A mutants and unaffected for G86A mutant. All presented altered amino acid uptake and transport associated currents in the presence of each of the cations (Na+, K+, Li+) that can be exploited by the wt. G87A mutant induced increased uncoupled fluxes in the presence of all the cations. Cross-linking studies, performed by the treatment of cysteine mutants with the oxidative complex Cu(Il)(l,10-phenanthroline)3, showed that limiting the flexibility of the region by covalent blockage of position 87, causes a significant reduction of amino acid uptake. Na+ protected G87C mutant from oxidation, both directly and indirectly. The conserved glycine triplet in KAAT1 plays therefore a complex role that allows initial steps of cation interaction with the transporter.
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Affiliation(s)
- M Giovanola
- Department of Molecular Sciences Applied to Biosystems, Universita degli Studi di Milano, Via Trentacoste 2, 20134 Milano, Italy
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Santacroce M, Castagna M, Sacchi VF. Passive water permeability of some wild type and mutagenized amino acid cotransporters of the SLC6/NSS family expressed in Xenopus laevis oocytes. Comp Biochem Physiol A Mol Integr Physiol 2010; 156:509-17. [PMID: 20394832 DOI: 10.1016/j.cbpa.2010.04.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2009] [Revised: 04/06/2010] [Accepted: 04/06/2010] [Indexed: 11/19/2022]
Abstract
In this paper passive water movement across the cell membrane mediated by wild type and mutagenized cotransporters was investigated. We evaluated water movement and, in parallel, amino acid uptake induced by some members of the SLC6/NSS family belonging to different kingdoms, namely the rat GABA transporter GAT1, the insect amino acid transporters KAAT1 and CAATCH1 and the bacterial leucine transporter LeuT, whose structure was recently solved. We also tested whether mutated proteins in which the solute translocation mechanism is altered or even abolished were able to induce water movement across cell membrane. The proteins of interest were expressed in Xenopus laevis oocytes and osmotic water permeabilities were estimated from the rate of cell volume change induced by an osmotic gradient in the absence of cotransported solutes. Under osmotic stress all the studied wild type amino acid cotransporters increased the water permeability of the membrane. The GABA transport inhibitor SKF 89976A inhibited both GABA transport and water movement induced by the expression of GAT1. Interestingly, the capacity of mutant proteins to induce water movement was not predictable on the basis of their substrate transport ability. In particular the GAT1 mutant Q291N, void of any transport activity, induced a water permeability similar to that induced by the wt protein. The KAAT1 mutant T339C, which showed a higher transport activity, induced a water permeability not significantly different from the wild type transporter. Interestingly, the bacterial leucine cotransporter LeuT, whose binding site for leucine and Na(+) is void of water, induced water movement through the plasma membrane.
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Affiliation(s)
- Massimo Santacroce
- Department of Molecular Sciences Applied to Biosystems, Università degli Studi di Milano, Milan, Italy.
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Forrest LR, Rudnick G. The rocking bundle: a mechanism for ion-coupled solute flux by symmetrical transporters. Physiology (Bethesda) 2010; 24:377-86. [PMID: 19996368 DOI: 10.1152/physiol.00030.2009] [Citation(s) in RCA: 215] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Crystal structures of the bacterial amino acid transporter LeuT have provided the basis for understanding the conformational changes associated with substrate translocation by a multitude of transport proteins with the same fold. Biochemical and modeling studies led to a "rocking bundle" mechanism for LeuT that was validated by subsequent transporter structures. These advances suggest how coupled solute transport might be defined by the internal symmetry of proteins containing inverted structural repeats.
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Affiliation(s)
- Lucy R Forrest
- Computational Structural Biology, Max Planck Institute for Biophysics, Frankfurt, Germany
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Castagna M, Bossi E, Sacchi VF. Molecular physiology of the insect K-activated amino acid transporter 1 (KAAT1) and cation-anion activated amino acid transporter/channel 1 (CAATCH1) in the light of the structure of the homologous protein LeuT. INSECT MOLECULAR BIOLOGY 2009; 18:265-279. [PMID: 19389142 DOI: 10.1111/j.1365-2583.2009.00881.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
K-activated amino acid transporter 1 (KAAT1) and cation-anion-activated amino acid transporter/channel 1 (CAATCH1) are amino acid cotransporters, belonging to the Na/Cl-dependent neurotransmitter transporter family (also called SLC6/NSS), that have been cloned from Manduca sexta midgut. They have been thoroughly studied by expression in Xenopus laevis oocytes, and structure/function analyses have made it possible to identify the structural determinants of their cation and amino acid selectivity. About 40 mutants of these proteins have been studied by measuring amino acid uptake and current/voltage relationships. The results obtained since the cloning of KAAT1 and CAATCH1 are here discussed in the light of the 3D model of the first crystallized member of the family, the leucine transporter LeuT.
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Affiliation(s)
- M Castagna
- Institute of General Physiology and Biological Chemistry 'G. Esposito', University of Milan, Milano, Italy
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