Structural and functional properties of the transporter SLC26A6 reveal mechanism of coupled anion exchange

Tippett, David N.; Breen, Colum; Butler, Stephen J.; Sawicka, Marta; Dutzler, Raimund

doi:10.1101/2023.03.06.531323

Cited by 4 publications

(11 citation statements)

References 41 publications

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“…This observation is in line with a recent report that R404V conferred a small, uncoupled chloride transport function on SLC26A6 (Tippett et al, 2023).…”

Section: Resultssupporting

confidence: 93%

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The molecular principles underlying diverse functions of the SLC26 family of proteins

Takahashi,

Homma

2023

Preprint

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Mammalian SLC26 proteins are membrane-based anion transporters that belong to the large SLC26/SulP family, and many of their variants are associated with hereditary diseases. Recent structural studies revealed a strikingly similar homodimeric molecular architecture for several SLC26 members, implying a shared molecular principle. Now a new question emerges as to how these structurally similar proteins execute diverse physiological functions. In this study we sought to identify the common vs. distinct molecular mechanism among the SLC26 proteins using both naturally occurring and artificial missense changes introduced to SLC26A4, SLC26A5, and SLC26A9. We found: (i) the basic residue at the anion binding site is essential for both anion antiport of SLC26A4 and motor functions of SLC26A5, and its conversion to a nonpolar residue is crucial but not sufficient for the fast uncoupled anion transport in SLC26A9; (ii) the conserved polar residues in the N- and C-terminal cytosolic domains are likely involved in dynamic hydrogen-bonding networks and are essential for anion antiport of SLC26A4 but not for motor (SLC26A5) and uncoupled anion transport (SLC26A9) functions; (iii) the hydrophobic interaction between each protomer’s last transmembrane helices, TM14, is not of functional significance in SLC26A9 but crucial for the functions of SLC26A4 and SLC26A5, likely contributing to optimally orient the axis of the relative movements of the core domain with respect to the gate domains within the cell membrane. These findings advance our understanding of the molecular mechanisms underlying the diverse physiological roles of the SLC26 family of proteins.

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“…This observation is in line with a recent report that R404V conferred a small, uncoupled chloride transport function on SLC26A6 (Tippett et al, 2023).…”

Section: Resultssupporting

confidence: 93%

“…1 , left), SLC26A5 (Bavi et al, 2021; Butan et al, 2022; Futamata et al, 2022; Ge et al, 2021) ( Fig. 1 , middle), SLC26A6 (Tippett et al, 2023), and SLC26A9 (Chi et al, 2020; Walter et al, 2019) ( Fig. 1 , right).…”

Section: Resultsmentioning

confidence: 99%

The molecular principles underlying diverse functions of the SLC26 family of proteins

Takahashi,

Homma

2023

Preprint

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“…A recent cryo-EM study on mouse pendrin (Liu et al, 2023) revealed a homodimeric architecture that is similar to prestin (Bavi et al, 2021; Butan et al, 2022; Futamata et al, 2022; Ge et al, 2021) and other SLC26 proteins (Chi et al, 2020; Tippett et al, 2023; Walter et al, 2019). The transmembrane domain consists of the gate and the core domains, and the ion translocation pathway is located in between them ( Fig.…”

Section: Resultsmentioning

confidence: 99%

Functional studies of deafness-associated pendrin and prestin variants

Takahashi,

Kojima,

Wasano

et al. 2024

Preprint

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Pendrin and prestin are evolutionary conserved membrane proteins that are essential for normal hearing. Pendrin is an anion transporter required for normal development and maintenance of ion homeostasis in the inner ear, while prestin is a voltage-dependent motor responsible for cochlear amplification essential for high sensitivity and frequency selectivity of mammalian hearing. Dysfunction of these proteins result in hearing loss in humans, and numerous deafness-associated pendrin and prestin variants have been identified in patients. However, the pathogenic impacts of many of these variants are ambiguous. Here we report results from our ongoing efforts in experimentally characterizing pendrin and prestin variants using in vitro functional assays, providing invaluable information regarding their pathogenicity.

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“…SLC26 anion exchangers form dimeric assemblies that can be demonstrated by structural studies (22,(43)(44)(45)(46)(47)(48) as well as by native gel electrophoresis (49). Since both experimental approaches do not exclude formation of higher oligomers, which are not sufficiently stable to tolerate solubilization/purification, we recently used a new dual-color colocalization (DCC) approach for the accurate determination of subunit stoichiometries of membrane proteins in situ (50,51).…”

Section: Discussionmentioning

confidence: 99%

Oligomerization and cellular localization of SLC26A11

Bungert-Plümke,

Guzman,

Fahlke

2024

Preprint

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The solute carrier family 26 (SLC26) encompasses multifunctional anion exchangers in all kingdoms of life. SLC26 proteins are known to assemble as dimers, and co-expression of multiple isoforms in certain cells raises the question of whether different SLC26s can assemble into hetero-dimers. We focused on SLC26A11, a broadly expressed isoform that differs from other isoforms in its subcellular localization. Whereas the vast majority of SLC26-FP fusion proteins, i.e., SLC26A1, SLC26A2, SlC26A3, SLC26A4/pendrin, SLC26A5/prestin, SLC26A6, SlC26A7, and SLC26A9, localize to the surface membrane of transfected mammalian cells, we found exclusive lysosomal localization of SLC26A11. Renal collecting duct intercalated cells express SLC26A11 together with SLC26A4/pendrin and SLC26A7, and we therefore tested whether heterodimerization between these transporters might result in SLC26 transporter re-localization. Neither in HEK293T nor in immortalized intercalated cells co-expressing SLC26A11 with SLC26A4/pendrin or with SLC26A7, changes in SLC26A11 localization were observed. Moreover, native gel electrophoresis did not provide any evidence for heterodimerization of these isoforms. We next tested heterodimerization of SLC26A11 with SLC26A1, SLC26A2, SLC26A6, or SLC26A9 via co-expression in HEK293T cells and confocal imaging. For all combinations, no changes in subcellular distribution were observed. We conclude that SLC26A11 does not heterodimerize with other SLC26 proteins and that heterodimerization does not target SLC26A11 to cellular surface membranes.

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Structural and functional properties of the transporter SLC26A6 reveal mechanism of coupled anion exchange

Cited by 4 publications

References 41 publications

The molecular principles underlying diverse functions of the SLC26 family of proteins

The molecular principles underlying diverse functions of the SLC26 family of proteins

Functional studies of deafness-associated pendrin and prestin variants

Oligomerization and cellular localization of SLC26A11

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