Cryo-EM structure of the calcium homeostasis modulator 1 channel

Ren, Yue; Wen, Tianlei; Xi, Zhiqin; Li, Shunjin; Lü, Jing; Zhang, Xing; Yang, Xue; Shen, Yuequan

doi:10.1126/sciadv.aba8161

Cited by 22 publications

(26 citation statements)

References 33 publications

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“…Recent single-particle cryo-EM studies determined the structures of various CALHMs including killifish CALHM1 and human CALHM2, 4, and 6, and provided insights into how CALHMs form and function as ion channels. 10,11,[36][37][38][39] On the contrary, the structure of CALHM3 is unknown. Protomers of CALHM1, 2, 4, and 6 possess 4 transmembrane helices with cytoplasmic Nand C-termini, and they exhibit diverse oligomeric assemblies from octamers to dodecamers.…”

Section: Discussionmentioning

confidence: 99%

Posttranslational regulation of CALHM1/3 channel: N ‐linked glycosylation and S ‐palmitoylation

et al. 2021

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Among calcium homeostasis modulator (CALHM) family members, CALHM1 and 3 together form a voltage-gated large-pore ion channel called CALHM1/3. CALHM1/3 plays an essential role in taste perception by mediating neurotransmitter release at channel synapses of taste bud cells. However, it is poorly understood how CALHM1/3 is regulated. Biochemical analyses of the two subunits following site-directed mutagenesis and pharmacological treatments established that both CALHM1 and 3 were N-glycosylated at single Asn residues in their second extracellular loops. Biochemical and electrophysiological studies revealed that N-glycan acquisition on CALHM1 and 3, respectively, controls the biosynthesis and gating kinetics of the CALHM1/3 channel. Furthermore, failure in subsequent remodeling of N-glycans decelerated the gating kinetics. Thus, the acquisition of N-glycans on both subunits and their remodeling differentially contribute to the functional expression of CALHM1/3. Meanwhile, metabolic labeling and acyl-biotin exchange assays combined with genetic modification demonstrated that CALHM3 was reversibly palmitoylated at three intracellular Cys residues. Screening of the DHHC protein acyltransferases identified DHHC3 and 15 as CALHM3 palmitoylating enzymes.The palmitoylation-deficient mutant CALHM3 showed a normal degradation rate and interaction with CALHM1. However, the same mutation markedly attenuated the channel activity but not surface localization of CALHM1/3, suggesting that CALHM3 palmitoylation is a critical determinant of CALHM1/3 activity but not its formation or forward trafficking. Overall, this study characterized N-glycosylation and S-palmitoylation of CALHM1/3 subunits and clarified their differential contributions to its functional expression, providing insights into the fine control of the CALHM1/3 channel and associated physiological processes.

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Section: Discussionmentioning

confidence: 99%

Posttranslational regulation of CALHM1/3 channel: N ‐linked glycosylation and S ‐palmitoylation

et al. 2021

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“…CALHM is regulated by membrane voltage and extracellular Ca 2+ concentration. Through convergent evolution, CALHM has structural features similar to connexins, pannexins, and innexins ( Siebert et al, 2013 ) which include four transmembrane helices with cytoplasmic amino and carboxyl termini, based on membrane topology prediction algorithms ( Demura et al, 2020 ; Ren et al, 2020 ). Human CALHM1 is predicted to be a membrane protein with 346 amino acids.…”

Section: Discussionmentioning

confidence: 99%

“…Human CALHM1 is predicted to be a membrane protein with 346 amino acids. The functional CALHM1 channel is a hexamer (two CALHM1 octamers) containing a functional pore with a diameter of ∼14 Å ( Ma et al, 2016 ; Demura et al, 2020 ; Ren et al, 2020 ). CALHM1 enables both cations and anions to go through due to its inability to discriminate between the two charged molecules.…”

Section: Discussionmentioning

confidence: 99%

“…Calcium homeostasis modulators (CALHM), including CALHM1 and CALHM2, are identified as a family of ion (cation and anion) channels and ATP channels in the plasma membrane that are sensitive to membrane voltage and extracellular Ca 2+ level ( Gallego-Sandin et al, 2011 ; Ma et al, 2012 , 2016 ; Siebert et al, 2013 ; Demura et al, 2020 ; Ren et al, 2020 ). In PAH, a rise in cytosolic free Ca 2+ concentration [(Ca 2+ ) cyt ] in PASMCs is not only a trigger for PASMC contraction and pulmonary vasoconstriction, but also a key stimulus for PASMC proliferation/migration and concentric pulmonary vascular remodeling ( Fernandez et al, 2015 ; Song et al, 2018 ).…”

Section: Introductionmentioning

confidence: 99%

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Upregulation of Calcium Homeostasis Modulators in Contractile-To-Proliferative Phenotypical Transition of Pulmonary Arterial Smooth Muscle Cells

Rodriguez¹,

Chen²,

Jain³

et al. 2021

Front. Physiol.

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Excessive pulmonary artery (PA) smooth muscle cell (PASMC) proliferation and migration are implicated in the development of pathogenic pulmonary vascular remodeling characterized by concentric arterial wall thickening and arteriole muscularization in patients with pulmonary arterial hypertension (PAH). Pulmonary artery smooth muscle cell contractile-to-proliferative phenotypical transition is a process that promotes pulmonary vascular remodeling. A rise in cytosolic Ca2+ concentration [(Ca2+)cyt] in PASMCs is a trigger for pulmonary vasoconstriction and a stimulus for pulmonary vascular remodeling. Here, we report that the calcium homeostasis modulator (CALHM), a Ca2+ (and ATP) channel that is allosterically regulated by voltage and extracellular Ca2+, is upregulated during the PASMC contractile-to-proliferative phenotypical transition. Protein expression of CALHM1/2 in primary cultured PASMCs in media containing serum and growth factors (proliferative PASMC) was significantly greater than in freshly isolated PA (contractile PASMC) from the same rat. Upregulated CALHM1/2 in proliferative PASMCs were associated with an increased ratio of pAKT/AKT and pmTOR/mTOR and an increased expression of the cell proliferation marker PCNA, whereas serum starvation and rapamycin significantly downregulated CALHM1/2. Furthermore, CALHM1/2 were upregulated in freshly isolated PA from rats with monocrotaline (MCT)-induced PH and in primary cultured PASMC from patients with PAH in comparison to normal controls. Intraperitoneal injection of CGP 37157 (0.6 mg/kg, q8H), a non-selective blocker of CALHM channels, partially reversed established experimental PH. These data suggest that CALHM upregulation is involved in PASMC contractile-to-proliferative phenotypical transition. Ca2+ influx through upregulated CALHM1/2 may play an important role in the transition of sustained vasoconstriction to excessive vascular remodeling in PAH or precapillary PH. Calcium homeostasis modulator could potentially be a target to develop novel therapies for PAH.

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“…Structural studies of CALHM family proteins have recently made great progress (Foskett, 2020). CALHM1 structures of several species have been reported to be octamers that do not form gap junctions due to N-glycosylation of the extracellular loop (Demura et al, 2020; Ren et al, 2020; Syrjanen et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Dynamic assembly of the calcium hemostasis modulator 1 channel gates ATP permeation

Ren

Wang

et al. 2021

Preprint

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Calcium hemostasis modulator 1 (CALHM1) is a voltage- and Ca2+-gated ATP channel that plays an important role in neuronal signaling. The currently reported CALHM structures are all in an ATP-conducting state, and the gating mechanism of ATP permeation remains elusive. Here, we report three cryo-EM reconstructions of heptameric CALHM1s with ordered or flexible long C-terminal helices and octameric CALHM1 with flexible long C-terminal helices at resolutions of 3.2 Å, 2.9 Å, and 3.5 Å. Structural analysis revealed that the heptameric CALHM1s are in an ATP nonconducting state in which the pore diameter in the middle is approximately 6.6 Å. Compared with those inside the octameric CALHM1s, the N-helices inside heptameric CALHM1s are in the "down" position to avoid steric clash with neighboring TM1 helices. MD simulations show that the pore size is significantly increased for ATP permeation during the movement of the N-helix from the "down" position to the "up" position. Therefore, we proposed a mechanism in which the "piston-like" motion of the N-helix drives the dynamic assembly of the CALHM1 channel for ATP permeation.

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Cryo-EM structure of the calcium homeostasis modulator 1 channel

Cited by 22 publications

References 33 publications

Posttranslational regulation of CALHM1/3 channel: N ‐linked glycosylation and S ‐palmitoylation

Posttranslational regulation of CALHM1/3 channel: N ‐linked glycosylation and S ‐palmitoylation

Upregulation of Calcium Homeostasis Modulators in Contractile-To-Proliferative Phenotypical Transition of Pulmonary Arterial Smooth Muscle Cells

Dynamic assembly of the calcium hemostasis modulator 1 channel gates ATP permeation

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