Dataset Information

The human MRS2 magnesium-binding domain is a regulatory feedback switch for channel activity.

ABSTRACT: Mitochondrial RNA splicing 2 (MRS2) forms a magnesium (Mg²⁺) entry protein channel in mitochondria. Whereas MRS2 contains two transmembrane domains constituting a pore on the inner mitochondrial membrane, most of the protein resides within the matrix. Yet, the precise structural and functional role of this obtrusive amino terminal domain (NTD) in human MRS2 is unknown. Here, we show that the MRS2 NTD self-associates into a homodimer, contrasting the pentameric assembly of CorA, an orthologous bacterial channel. Mg²⁺ and calcium suppress lower and higher order oligomerization of MRS2 NTD, whereas cobalt has no effect on the NTD but disassembles full-length MRS2. Mutating-pinpointed residues-mediating Mg²⁺ binding to the NTD not only selectively decreases Mg²⁺-binding affinity ∼sevenfold but also abrogates Mg²⁺ binding-induced secondary, tertiary, and quaternary structure changes. Disruption of NTD Mg²⁺ binding strikingly potentiates mitochondrial Mg²⁺ uptake in WT and Mrs2 knockout cells. Our work exposes a mechanism for human MRS2 autoregulation by negative feedback from the NTD and identifies a novel gain of function mutant with broad applicability to future Mg²⁺ signaling research.

SUBMITTER: Uthayabalan S

PROVIDER: S-EPMC9909464 | biostudies-literature | 2023 Apr

REPOSITORIES: biostudies-literature

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The human MRS2 magnesium-binding domain is a regulatory feedback switch for channel activity.

Uthayabalan Sukanthathulse S Vishnu Neelanjan N Madesh Muniswamy M Stathopulos Peter B PB

Life science alliance 20230208 4

Mitochondrial RNA splicing 2 (MRS2) forms a magnesium (Mg<sup>2+</sup>) entry protein channel in mitochondria. Whereas MRS2 contains two transmembrane domains constituting a pore on the inner mitochondrial membrane, most of the protein resides within the matrix. Yet, the precise structural and functional role of this obtrusive amino terminal domain (NTD) in human MRS2 is unknown. Here, we show that the MRS2 NTD self-associates into a homodimer, contrasting the pentameric assembly of CorA, an ort ...[more]

PMID: 36754568

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Project description:TRPM7 is a Ca(2+)- and Mg(2+)-permeable cation channel that also contains a protein kinase domain. While there is general consensus that the channel is inhibited by free intracellular Mg(2+), the functional roles of intracellular levels of Mg.ATP and the kinase domain in regulating TRPM7 channel activity have been discussed controversially. To obtain insight into these issues, we have determined the effect of purine and pyrimidine magnesium nucleotides on TRPM7 currents and investigated the possible involvement of the channel's kinase domain in mediating them. We report here that physiological Mg.ATP concentrations can inhibit TRPM7 channels and strongly enhance the channel blocking efficacy of free Mg(2+). Mg.ADP, but not AMP, had similar, albeit smaller effects, indicating a double protection against possible Mg(2+) and Ca(2+) overflow during variations of cell energy levels. Furthermore, nearly all Mg-nucleotides were able to inhibit TRPM7 activity to varying degrees with the following rank in potency: ATP > TTP > CTP > or = GTP > or = UTP > ITP approximately free Mg(2+) alone. These nucleotides also enhanced TRPM7 inhibition by free Mg(2+), suggesting the presence of two interacting binding sites that jointly regulate TRPM7 channel activity. Finally, the nucleotide-mediated inhibition was lost in phosphotransferase-deficient single-point mutants of TRPM7, while the Mg(2+)-dependent regulation was retained with reduced efficacy. Interestingly, truncated mutant channels with a complete deletion of the kinase domain regained Mg.NTP sensitivity; however, this inhibition did not discriminate between nucleotide species, suggesting that the COOH-terminal truncation exposes the previously inaccessible Mg(2+) binding site to Mg-nucleotide binding without imparting nucleotide specificity. We conclude that the nucleotide-dependent regulation of TRPM7 is mediated by the nucleotide binding site on the channel's endogenous kinase domain and interacts synergistically with a Mg(2+) binding site extrinsic to that domain.

Dataset Information

The human MRS2 magnesium-binding domain is a regulatory feedback switch for channel activity.

Publications

The human MRS2 magnesium-binding domain is a regulatory feedback switch for channel activity.

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