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Bhatt M, Di Iacovo A, Romanazzi T, Roseti C, Cinquetti R, Bossi E. The "www" of Xenopus laevis Oocytes: The Why, When, What of Xenopus laevis Oocytes in Membrane Transporters Research. MEMBRANES 2022; 12:membranes12100927. [PMID: 36295686 PMCID: PMC9610376 DOI: 10.3390/membranes12100927] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 09/22/2022] [Accepted: 09/23/2022] [Indexed: 05/16/2023]
Abstract
After 50 years, the heterologous expression of proteins in Xenopus laevis oocytes is still essential in many research fields. New approaches and revised protocols, but also classical methods, such as the two-electrode voltage clamp, are applied in studying membrane transporters. New and old methods for investigating the activity and the expression of Solute Carriers (SLC) are reviewed, and the kinds of experiment that are still useful to perform with this kind of cell are reported. Xenopus laevis oocytes at the full-grown stage have a highly efficient biosynthetic apparatus that correctly targets functional proteins at the defined compartment. This small protein factory can produce, fold, and localize almost any kind of wild-type or recombinant protein; some tricks are required to obtain high expression and to verify the functionality. The methodologies examined here are mainly related to research in the field of membrane transporters. This work is certainly not exhaustive; it has been carried out to be helpful to researchers who want to quickly find suggestions and detailed indications when investigating the functionality and expression of the different members of the solute carrier families.
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Affiliation(s)
- Manan Bhatt
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, Via Dunant 3, 21100 Varese, Italy
- Experimental and Translational Medicine, University of Insubria, Via Ottorino Rossi 9, 21100 Varese, Italy
| | - Angela Di Iacovo
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, Via Dunant 3, 21100 Varese, Italy
- Experimental and Translational Medicine, University of Insubria, Via Ottorino Rossi 9, 21100 Varese, Italy
| | - Tiziana Romanazzi
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, Via Dunant 3, 21100 Varese, Italy
- Experimental and Translational Medicine, University of Insubria, Via Ottorino Rossi 9, 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
- Centre for Neuroscience—Via Manara 7, University of Insubria, 21052 Busto Arsizio, Italy
| | - Raffaella Cinquetti
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, Via Dunant 3, 21100 Varese, Italy
| | - Elena Bossi
- Laboratory of Cellular and Molecular Physiology, Department of Biotechnology and Life Sciences, University of Insubria, Via Dunant 3, 21100 Varese, Italy
- Centre for Neuroscience—Via Manara 7, University of Insubria, 21052 Busto Arsizio, Italy
- Correspondence:
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2
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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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Holtof M, Lenaerts C, Cullen D, Vanden Broeck J. Extracellular nutrient digestion and absorption in the insect gut. Cell Tissue Res 2019; 377:397-414. [DOI: 10.1007/s00441-019-03031-9] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Accepted: 04/04/2019] [Indexed: 02/07/2023]
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4
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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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Tang X, Liu H, Chen Q, Wang X, Xiong Y, Zhao P. Genome-Wide Identification, Characterization and Expression Analysis of the Solute Carrier 6 Gene Family in Silkworm (Bombyx mori). Int J Mol Sci 2016; 17:ijms17101675. [PMID: 27706106 PMCID: PMC5085708 DOI: 10.3390/ijms17101675] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 09/26/2016] [Indexed: 11/16/2022] Open
Abstract
The solute carrier 6 (SLC6) gene family, initially known as the neurotransmitter transporters, plays vital roles in the regulation of neurotransmitter signaling, nutrient absorption and motor behavior. In this study, a total of 16 candidate genes were identified as SLC6 family gene homologs in the silkworm (Bombyx mori) genome. Spatio-temporal expression patterns of silkworm SLC6 gene transcripts indicated that these genes were highly and specifically expressed in midgut, brain and gonads; moreover, these genes were expressed primarily at the feeding stage or adult stage. Levels of expression for most midgut-specific and midgut-enriched gene transcripts were down-regulated after starvation but up-regulated after re-feeding. In addition, we observed that expression levels of these genes except for BmSLC6-15 and BmGT1 were markedly up-regulated by a juvenile hormone analog. Moreover, brain-enriched genes showed differential expression patterns during wandering and mating processes, suggesting that these genes may be involved in modulating wandering and mating behaviors. Our results improve our understanding of the expression patterns and potential physiological functions of the SLC6 gene family, and provide valuable information for the comprehensive functional analysis of the SLC6 gene family.
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Affiliation(s)
- Xin Tang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China.
| | - Huawei Liu
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China.
| | - Quanmei Chen
- Department of Biochemistry and Molecular Biology, Chongqing Medical University, Chongqing 400016, China.
| | - Xin Wang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China.
- Chongqing Engineering and Technology Research Center for Novel Silk Materials, Chongqing 400715, China.
| | - Ying Xiong
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China.
| | - Ping Zhao
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China.
- Chongqing Engineering and Technology Research Center for Novel Silk Materials, Chongqing 400715, China.
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Vollero A, Imperiali FG, Cinquetti R, Margheritis E, Peres A, Bossi E. The D-amino acid transport by the invertebrate SLC6 transporters KAAT1 and CAATCH1 from Manduca sexta. Physiol Rep 2016; 4:4/4/e12691. [PMID: 26884475 PMCID: PMC4759042 DOI: 10.14814/phy2.12691] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The ability of the SLC6 family members, the insect neutral amino acid cotransporter KAAT1(K+‐coupled amino acid transporter 1) and its homologous CAATCH1(cation anion activated amino acid transporter/channel), to transport D‐amino acids has been investigated through heterologous expression in Xenopus laevis oocytes and electrophysiological techniques. In the presence of D‐isomers of leucine, serine, and proline, the msKAAT1 generates inward, transport‐associated, currents with variable relative potencies, depending on the driving ion Na+ or K+. Higher concentrations of D‐leucine (≥1 mmol/L) give rise to an anomalous response that suggests the existence of a second binding site with inhibitory action on the transport process. msCAATCH1 is also able to transport the D‐amino acids tested, including D‐leucine, whereas L‐leucine acts as a blocker. A similar behavior is exhibited by the KAAT1 mutant S308T, confirming the relevance of the residue in this position in L‐leucine binding and the different interaction of D‐leucine with residues involved in transport mechanism. D‐leucine and D‐serine on various vertebrate orthologs B0AT1 (SLC6A19) elicited only a very small current and singular behavior was not observed, indicating that it is specific of the insect neutral amino acid transporters. These findings highlight the relevance of D‐amino acid absorption in the insect nutrition and metabolism and may provide new evidences in the molecular transport mechanism of SLC6 family.
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Affiliation(s)
- Alessandra Vollero
- Department of Biotechnology and Life Sciences, University of Insubria, Varese, Italy
| | - Francesca G Imperiali
- Department of Biotechnology and Life Sciences, University of Insubria, Varese, Italy
| | - Raffaella Cinquetti
- Department of Biotechnology and Life Sciences, University of Insubria, Varese, Italy
| | - Eleonora Margheritis
- Department of Biotechnology and Life Sciences, University of Insubria, Varese, Italy
| | - Antonio Peres
- Department of Biotechnology and Life Sciences, University of Insubria, Varese, Italy
| | - Elena Bossi
- Department of Biotechnology and Life Sciences, University of Insubria, Varese, Italy Interuniversity Center "The ProteinFactory", Politecnico di Milano, ICRM-CNR Milano and Università dell'Insubria, Milan, Italy
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7
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Fu KY, Guo WC, Ahmat T, Li GQ. Knockdown of a nutrient amino acid transporter gene LdNAT1 reduces free neutral amino acid contents and impairs Leptinotarsa decemlineata pupation. Sci Rep 2015; 5:18124. [PMID: 26657797 PMCID: PMC4676043 DOI: 10.1038/srep18124] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 11/12/2015] [Indexed: 11/09/2022] Open
Abstract
A Leptinotarsa decemlineata SLC6 NAT gene (LdNAT1) was cloned. LdNAT1 was highly expressed in the larval alimentary canal especially midgut. LdNAT1 mRNA levels were high right after the molt and low just before the molt. JH and a JH analog pyriproxyfen activated LdNAT1 expression. RNAi of an allatostatin gene LdAS-C increased JH and upregulated LdNAT1 transcription. Conversely, silencing of a JH biosynthesis gene LdJHAMT decreased JH and reduced LdNAT1 expression. Moreover, 20E and an ecdysteroid agonist halofenozide repressed LdNAT1 expression, whereas a decrease in 20E by RNAi of an ecdysteroidogenesis gene LdSHD and disruption of 20E signaling by knockdown of LdE75 and LdFTZ-F1 activated LdNAT1 expression. Thus, LdNAT1 responded to both 20E and JH. Moreover, knockdown of LdNAT1 reduced the contents of cysteine, histidine, isoleucine, leucine, methionine, phenylalanine and serine in the larval bodies and increased the contents of these amino acids in the larval feces. Furthermore, RNAi of LdNAT1 inhibited insulin/target of rapamycin pathway, lowered 20E and JH titers, reduced 20E and JH signaling, retarded larval growth and impaired pupation. These data showed that LdNAT1 was involved in the absorption of several neutral amino acids critical for larval growth and metamorphosis.
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Affiliation(s)
- Kai-Yun Fu
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
| | - Wen-Chao Guo
- Department of Plant Protection, Xinjiang Academy of Agricultural Sciences; Urumqi 830091, China
| | - Tursun Ahmat
- Department of Plant Protection, Xinjiang Academy of Agricultural Sciences; Urumqi 830091, China
| | - Guo-Qing Li
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
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8
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Wan PJ, Fu KY, Lü FG, Wang XX, Guo WC, Li GQ. Knocking down a putative Δ(1) -pyrroline-5-carboxylate dehydrogenase gene by RNA interference inhibits flight and causes adult lethality in the Colorado potato beetle Leptinotarsa decemlineata (Say). PEST MANAGEMENT SCIENCE 2015; 71:1387-96. [PMID: 25400271 DOI: 10.1002/ps.3941] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Revised: 10/07/2014] [Accepted: 11/09/2014] [Indexed: 05/06/2023]
Abstract
BACKGROUND Leptinotarsa decemlineata is an able disperser by flight. Novel control strategies must be explored to control the damage and inhibit the dispersal efficiently. Proline is a major energy substrate during flight. Δ-Pyrroline-5-carboxylate dehydrogenase (P5CDh) catalyses the second step of proline degradation for the production of ATP. RESULTS A full-length Ldp5cdh cDNA was cloned. Ldp5cdh was ubiquitously expressed in the eggs, the first through fourth larval instars, wandering larvae, pupae and adults. In the adults, Ldp5cdh mRNA was widely distributed in thorax muscles, midgut, foregut, hindgut, Malpighian tubules, ventral ganglion, fat body and epidermis, with the expression levels from the highest to the lowest. Two double-stranded RNAs (dsRNAs) (dsLdp5cdh1 and dsLdp5cdh2) targeting Ldp5cdh were constructed and bacterially expressed. Ingestion of dsLdp5cdh1 and dsLdp5cdh2 successfully silenced Ldp5cdh, significantly increased the contents of proline, arginine and alanine, but strongly decreased the contents of asparate, asparagine, glutamate and glutamine in the haemolymph. Moreover, knocking down Ldp5cdh significantly reduced ATP content, decreased flight speed, shortened flight distance and increased adult mortality. CONCLUSIONS It seems that identified Ldp5cdh encodes a functional P5CDh enzyme, and Ldp5cdh may serve as a potential target for dsRNA-based pesticide for controlling the damage and dispersal of L. decemlineata adults. © 2014 Society of Chemical Industry.
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Affiliation(s)
- Pin-Jun Wan
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing, China
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou, China
| | - Kai-Yun Fu
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Feng-Gong Lü
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Xin-Xin Wang
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - Wen-Chao Guo
- Department of Plant Protection, Xinjiang Academy of Agricultural Sciences, Urumqi, China
| | - Guo-Qing Li
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing, China
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9
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Fu KY, Guo WC, Lü FG, Liu XP, Li GQ. Response of the vacuolar ATPase subunit E to RNA interference and four chemical pesticides in Leptinotarsa decemlineata (Say). PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY 2014; 114:16-23. [PMID: 25175645 DOI: 10.1016/j.pestbp.2014.07.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Revised: 07/20/2014] [Accepted: 07/20/2014] [Indexed: 06/03/2023]
Abstract
Vacuolar-type H(+)-ATPases (vATPases) are localized in the apical membranes of nearly all epithelial tissues of insects, energize the membranes to absorb and/or secrete ions and fluids, and play essential roles in many physiological functions. Here we cloned and characterized a 1041-bp full-length vATPase subunit E cDNA (named as LdATPaseE) that encoded a 226-amino acid protein in Leptinotarsa decemlineata. LdATPaseE mRNA levels were constantly increased from egg to the third- and fourth-instar stages, dropped in wandering and pupal stages and were elevated again in the adult stage. It was highly expressed in ileum and rectum, moderately expressed in Malpighian tubules, midgut and foregut, and lowly expressed in fat body, ventral ganglion, epidermis and haemocytes in the fourth instars. After continuously ingested double-stranded RNAs originated from two LdATPaseE fragments LdATPaseE1 and LdATPaseE2, the target mRNA levels in the larvae were reduced by 85% and 55%, the larval growth and survival were significantly affected. Furthermore, topical application of fipronil, butane-fipronil, endosulfan and cypermethrin significantly upregulated LdATPaseE expression up to 8.3, 4.2, 2.8 and 6.2-fold 1 day after experiment, and up to 15.8, 3.4, 3.6 and 4.5-fold 2 days after treatment. It seems that depletion of vATPase subunit E is lethal, indicating that targeting vATPases by dsRNA appears a promising means of combating L. decemlineata. Moreover, vATPase subunit E is a pesticide inducible gene and may play a role in pesticide toxicity.
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Affiliation(s)
- Kai-Yun Fu
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China.
| | - Wen-Chao Guo
- Department of Plant Protection, Xinjiang Academy of Agricultural Sciences, Urumqi 830091, China.
| | - Feng-gong Lü
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China.
| | - Xin-ping Liu
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China.
| | - Guo-qing Li
- Education Ministry Key Laboratory of Integrated Management of Crop Diseases and Pests, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China.
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10
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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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Characterization of the transport of lysine-containing dipeptides by PepT1 orthologs expressed in Xenopus laevis oocytes. Comp Biochem Physiol A Mol Integr Physiol 2012; 164:520-8. [PMID: 23268205 DOI: 10.1016/j.cbpa.2012.12.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Revised: 12/13/2012] [Accepted: 12/17/2012] [Indexed: 11/23/2022]
Abstract
During digestion, dietary proteins cleaved in di and tri-peptides are translocated from the intestinal lumen into the enterocytes via PepT1 (SLC15A1) using an inwardly directed proton electrochemical gradient. The kinetic properties in various PepT1 orthologs (Dicentrarchus labrax, Oryctolagus cuniculus, Danio rerio) have been explored to determine the transport efficiency of different combinations of lysine, methionine, and glycine. Species-specific differences were observed. Lys-Met resulted the best substrate at all tested potentials in sea bass and rabbit PepT1, whereas in the zebrafish transporter all tested dipeptides (except Gly-Lys) elicited similar currents independently on the charge position or amino acid composition. For the sea bass and rabbit PepT1, kinetic parameters, K(0.5) and I(max) and their ratio, show the importance of the position of the charged lysine in the peptide. The PepT1 transporter of these species has very low affinity for Lys-Lys and Gly-Lys; this reduces the transport efficiency which is instead higher for Lys-Met and Lys-Gly. PepT1 from zebrafish showed relatively high affinity and excellent transport efficiency for Met-Lys and Lys-Met. These data led us to speculate about the structural determinants involved in substrate interaction according to the model proposed for this transporter.
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12
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An inverse relationship links temperature and substrate apparent affinity in the ion-coupled cotransporters rGAT1 and KAAT1. Int J Mol Sci 2012; 13:15565-74. [PMID: 23443081 PMCID: PMC3546649 DOI: 10.3390/ijms131215565] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Revised: 11/14/2012] [Accepted: 11/15/2012] [Indexed: 01/20/2023] Open
Abstract
The effects of temperature on the operation of two ion-coupled cotransporters of the SLC6A family, namely rat GAT1 (SLC6A1) and KAAT1 (SLC6A19) from Manduca sexta, have been studied by electrophysiological means in Xenopus laevis oocytes expressing these proteins. The maximal transport-associated current (Imax) and the apparent substrate affinity (K05) were measured. In addition to the expected increase in transport rate (Q10 = 3–6), both transporters showed greater K05 values (i.e., a decrease in apparent affinity) at higher temperatures. The transport efficiency, estimated as Imax/K05, increased at negative potentials in both transporters, but did not show statistically significant differences with temperature. The observation that the apparent substrate affinity is inversely related to the transport rate suggests a kinetic regulation of this parameter. Furthermore, the present results indicate that the affinities estimated at room temperature for mammalian cotransporters may not be simply extrapolated to their physiological operating conditions.
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13
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Boudko DY. Molecular basis of essential amino acid transport from studies of insect nutrient amino acid transporters of the SLC6 family (NAT-SLC6). JOURNAL OF INSECT PHYSIOLOGY 2012; 58:433-49. [PMID: 22230793 PMCID: PMC3397479 DOI: 10.1016/j.jinsphys.2011.12.018] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Revised: 12/21/2011] [Accepted: 12/23/2011] [Indexed: 05/03/2023]
Abstract
Two protein families that represent major components of essential amino acid transport in insects have been identified. They are annotated as the SLC6 and SLC7 families of transporters according to phylogenetic proximity to characterized amino acid transporters (HUGO nomenclature). Members of these families have been identified as important apical and basolateral parts of transepithelial essential amino acid absorption in the metazoan alimentary canal. Synergistically, they play critical physiological roles as essential substrate providers to diverse metabolic processes, including generic protein synthesis. This review briefly clarifies the requirements for amino acid transport and a variety of amino acid transport mechanisms, including the aforementioned families. Further it focuses on the large group of Nutrient Amino acid Transporters (NATs), which comprise a recently identified subfamily of the Neurotransmitter Sodium Symporter family (NSS or SLC6). The first insect NAT, cloned from the caterpillar gut, has a broad substrate spectrum similar to mammalian B(0) transporters. Several new NAT-SLC6 members have been characterized in an effort to explore mechanisms for the essential amino acid absorption in model dipteran insects. The identification and functional characterization of new B(0)-like and narrow specificity transporters of essential amino acids in fruit fly and mosquitoes leads to a fundamentally important insight: that NATs evolved and act together as the integrated active core of a transport network that mediates active alimentary absorption and systemic distribution of essential amino acids. This role of NATs is projected from the most primitive prokaryotes to the most complex metazoan organisms, and represents an interesting platform for unraveling the molecular evolution of amino acid transport and modeling amino acid transport disorders. The comparative study of NATs elucidates important adaptive differences between essential amino acid transportomes of invertebrate and vertebrate organisms, outlining a new possibility for selective targeting of essential amino acid absorption mechanisms to control medically and economically important arthropods and other invertebrate organisms.
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Affiliation(s)
- Dmitri Y Boudko
- Department of Physiology and Biophysics of Rosalind Franklin University, Chicago Medical School, North Chicago, IL 60064, USA.
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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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