The Polar T1 Interface Is Linked to Conformational Changes that Open the Voltage-Gated Potassium Channel

Minor, Daniel L.; Lin, Yu-Fung; Mobley, B.C.; Avelar, A.; Jan, Yuh Nung; Berger, James M.

doi:10.1016/s0092-8674(00)00088-x

Cited by 179 publications

(194 citation statements)

References 60 publications

(4 reference statements)

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“…How can the oligomerization͞trafficking competence of TRPM6 be affected by mutation of S141, which is located far away from the putative transmembrane segment? It is tempting to speculate that the TRPM N terminus serves a similar role for the multimerization of ion channel subunits as the N-terminal T1 domains in voltage-gated K ϩ channels (24).…”

Section: Discussionmentioning

confidence: 99%

Disruption of TRPM6/TRPM7 complex formation by a mutation in the TRPM6 gene causes hypomagnesemia with secondary hypocalcemia

Chubanov

Waldegger

Schnitzler

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

343

385

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Impaired magnesium reabsorption in patients with TRPM6 gene mutations stresses an important role of TRPM6 (melastatin-related TRP cation channel) in epithelial magnesium transport. While attempting to isolate full-length TRPM6, we found that the human TRPM6 gene encodes multiple mRNA isoforms. Full-length TRPM6 variants failed to form functional channel complexes because they were retained intracellularly on heterologous expression in HEK 293 cells and Xenopus oocytes. However, TRPM6 specifically interacted with its closest homolog, the Mg 2؉ -permeable cation channel TRPM7, resulting in the assembly of functional TRPM6͞TRPM7 complexes at the cell surface. The naturally occurring S141L TRPM6 missense mutation abrogated the oligomeric assembly of TRPM6, thus providing a cell biological explanation for the human disease. Together, our data suggest an important contribution of TRPM6͞ TRPM7 heterooligomerization for the biological role of TRPM6 in epithelial magnesium absorption.I nvestigations on Drosophila flies with impaired vision due to mutations in the transient receptor potential gene (trp) initiated a search for homologous proteins in mammals, leading to the discovery of three subfamilies of cation channels: TRPCs (canonical or classical TRPs), TRPVs (vanilloid receptor and related proteins), and TRPMs (melastatin and related proteins) (1, 2). TRPC channels mediate cation entry in response to phospholipase C activation, whereas TRPV proteins respond to physical and chemical stimuli, such as temperature, pH, and mechanical stress (3, 4). Within their respective subfamilies, TRPCs and TRPVs form homo-and heterotetramers displaying novel pore properties when compared to their homomultimeric counterparts (1, 5-9). The eight TRPM family members differ significantly from the aforementioned TRP channels in terms of domain structure, cation selectivity, and activation mechanisms (3, 10). Two TRPM proteins, TRPM6 and TRPM7, harbor serine͞threonine kinase domains in their C termini (11-16). Furthermore, TRPM7 displays unusual permeation properties by conducting a range of divalent metal ions including Mg 2ϩ and Mn 2ϩ (13,17,18).It was recently shown that autosomal recessive hypomagnesemia with secondary hypocalcemia (HSH) is caused by mutations in the TRPM6 gene (15,16). HSH is characterized by low serum Mg 2ϩ levels due to defective intestinal absorption or͞and renal wasting of Mg 2ϩ . Here we demonstrate that TRPM6 requires assembly with TRPM7 to form channel complexes in the cell membrane and that disruption of multimer formation by a mutated TRPM6 variant, TRPM6(S141L), results in human disease. MethodsMolecular Biology and Generation of TRPM6 Polyclonal Antisera. The cloning procedure of human TRPM6 isoforms (Table 1) as well as amplification of other TRPM cDNAs is described in detail in Supporting Methods, which is published as supporting information on the PNAS web site. For TRPM proteins C-terminally fused to cyan (CFP) or yellow (YFP) fluorescent proteins, STOP codons in TRPMs were replaced by XhoI restrictio...

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Section: Discussionmentioning

confidence: 99%

Disruption of TRPM6/TRPM7 complex formation by a mutation in the TRPM6 gene causes hypomagnesemia with secondary hypocalcemia

Chubanov

Waldegger

Schnitzler

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

343

385

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“…This multipurpose domain, which also serves as a docking station for intracellular auxiliary proteins (3,5,(33)(34)(35) and has been implicated in channel trafficking (36) and gating (14,15,37,38), acts at early stages of assembly when the peptide chains are still attached to ribosomes (39). The function of the T1 domain in the assembly process is 2-fold, providing stabilizing interactions for some, and prohibiting the interaction of other subunits.…”

Section: Discussionmentioning

confidence: 99%

Fluorescence measurements reveal stoichiometry of K ⁺ channels formed by modulatory and delayed rectifier α-subunits

Kerschensteiner

Soto

Stocker

2005

Proc. Natl. Acad. Sci. U.S.A.

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Modulatory ␣-subunits, which comprise one-fourth of all voltagegated K ؉ channel (Kv) ␣-subunits, do not assemble into homomeric channels, but selectively associate with delayed rectifier Kv2 subunits to form heteromeric channels of unknown stoichiometry. Their distinct expression patterns and unique functional properties have made these channels candidate molecular correlates for a broad set of native K ؉ currents. Here, we combine FRET and electrophysiological measurements to determine the stoichiometry and geometry of heteromeric channels composed of the delayed rectifier Kv2.1 subunit and the modulatory Kv9.3 ␣-subunit. Kv channel ␣-subunits were fused with GFP variants, and heteromerization of different combinations of tagged and untagged ␣-subunits was studied. FRET, evaluated by acceptor photobleaching, was only observed upon formation of functional channels. Our results, obtained from two independent experimental paradigms, suggest the formation of heteromeric Kv2.1͞Kv9.3 channels of fixed stoichiometry consisting of three Kv2.1 subunits and one Kv9.3 subunit. Strikingly, despite this uneven stoichiometry, we find that heteromeric Kv2.1͞Kv9.3 channels maintain a pseudosymmetric arrangement of subunits around the central pore.FRET ͉ voltage-gated K ϩ channel ͉ potassium channel ͉ silent subunit

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“…In the case of the voltage-gated K + channel (Kv), electrophysiological studies with toxin blockers showed the functional unit to be a tetramer 11 , a finding that was confirmed by X-ray crystallography [12][13][14][15] . Assembly of the four subunits into the tetrameric channel forms the permeation pathway in the centre.…”

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confidence: 89%

The cytoplasmic coiled-coil mediates cooperative gating temperature sensitivity in the voltage-gated H+ channel Hv1

et al. 2012

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Hv1/VsoP is a dimeric voltage-gated H + channel in which the gating of one subunit is reportedly coupled to that of the other subunit within the dimer. The molecular basis for dimer formation and intersubunit coupling, however, remains unknown. Here we show that the carboxy terminus ends downstream of the s4 voltage-sensor helix twist in a dimer coiled-coil architecture, which mediates cooperative gating. We also show that the temperature-dependent activation of H + current through Hv1/VsoP is regulated by thermostability of the coiled-coil domain, and that this regulation is altered by mutation of the linker between s4 and the coiled-coil. Cooperative gating within the dimer is also dependent on the linker structure, which circular dichroism spectrum analysis suggests is α-helical. our results indicate that the cytoplasmic coiled-coil strands form continuous α-helices with s4 and mediate cooperative gating to adjust the range of temperatures over which Hv1/VsoP operates.

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The Polar T1 Interface Is Linked to Conformational Changes that Open the Voltage-Gated Potassium Channel

Cited by 179 publications

References 60 publications

Disruption of TRPM6/TRPM7 complex formation by a mutation in the TRPM6 gene causes hypomagnesemia with secondary hypocalcemia

Disruption of TRPM6/TRPM7 complex formation by a mutation in the TRPM6 gene causes hypomagnesemia with secondary hypocalcemia

Fluorescence measurements reveal stoichiometry of K ⁺ channels formed by modulatory and delayed rectifier α-subunits

The cytoplasmic coiled-coil mediates cooperative gating temperature sensitivity in the voltage-gated H+ channel Hv1

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The Polar T1 Interface Is Linked to Conformational Changes that Open the Voltage-Gated Potassium Channel

Cited by 179 publications

References 60 publications

Disruption of TRPM6/TRPM7 complex formation by a mutation in the TRPM6 gene causes hypomagnesemia with secondary hypocalcemia

Disruption of TRPM6/TRPM7 complex formation by a mutation in the TRPM6 gene causes hypomagnesemia with secondary hypocalcemia

Fluorescence measurements reveal stoichiometry of K + channels formed by modulatory and delayed rectifier α-subunits

The cytoplasmic coiled-coil mediates cooperative gating temperature sensitivity in the voltage-gated H+ channel Hv1

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Fluorescence measurements reveal stoichiometry of K ⁺ channels formed by modulatory and delayed rectifier α-subunits