scholarly journals The D50N mutation and syndromic deafness: Altered Cx26 hemichannel properties caused by effects on the pore and intersubunit interactions

2013 ◽  
Vol 142 (1) ◽  
pp. 3-22 ◽  
Author(s):  
Helmuth A. Sanchez ◽  
Krista Villone ◽  
Miduturu Srinivas ◽  
Vytas K. Verselis
Keyword(s):  
Sensorineural Deafness ◽  
Gjb2 Gene ◽  
Loss Of Function ◽  
Impact Function ◽  
Corneal Inflammation ◽  
Extracellular Region ◽  
Intersubunit Interactions ◽  
Pore Lining ◽  
Electrostatic Mechanism ◽  
Insight Into

Mutations in the GJB2 gene, which encodes Cx26, are the most common cause of sensorineural deafness. In syndromic cases, such as keratitis-ichthyosis-deafness (KID) syndrome, in which deafness is accompanied by corneal inflammation and hyperkeratotic skin, aberrant hemichannel function has emerged as the leading contributing factor. We found that D50N, the most frequent mutation associated with KID syndrome, produces multiple aberrant hemichannel properties, including loss of inhibition by extracellular Ca2+, decreased unitary conductance, increased open hemichannel current rectification and voltage-shifted activation. We demonstrate that D50 is a pore-lining residue and that negative charge at this position strongly influences open hemichannel properties. Examination of two putative intersubunit interactions involving D50 suggested by the Cx26 crystal structure, K61–D50 and Q48–D50, showed no evidence of a K61–D50 interaction in hemichannels. However, our data suggest that Q48 and D50 interact and disruption of this interaction shifts hemichannel activation positive along the voltage axis. Additional shifts in activation by extracellular Ca2+ remained in the absence of a D50–Q48 interaction but required an Asp or Glu at position 50, suggesting a separate electrostatic mechanism that critically involves this position. In gap junction (GJ) channels, D50 substitutions produced loss of function, whereas K61 substitutions functioned as GJ channels but not as hemichannels. These data demonstrate that D50 exerts effects on Cx26 hemichannel and GJ channel function as a result of its dual role as a pore residue and a component of an intersubunit complex in the extracellular region of the hemichannel. Differences in the effects of substitutions in GJ channels and hemichannels suggest that perturbations in structure occur upon hemichannel docking that significantly impact function. Collectively, these data provide insight into Cx26 structure–function and the underlying bases for the phenotypes associated with KID syndrome patients carrying the D50N mutation.

scholarly journals Converging physiological roles of the anthrax toxin receptors

F1000Research ◽  
2019 ◽  
Vol 8 ◽  
pp. 1415
Author(s):  
Oksana A. Sergeeva ◽  
F. Gisou van der Goot
Keyword(s):  
Anthrax Toxin ◽  
Loss Of Function ◽  
Disease Symptoms ◽  
Hyaline Fibromatosis Syndrome ◽  
Anthrax Toxins ◽  
The Difference ◽  
Related Proteins ◽  
Tumor Endothelial Marker 8 ◽  
Insight Into ◽  
Shed Light

The anthrax toxin receptors—capillary morphogenesis gene 2 (CMG2) and tumor endothelial marker 8 (TEM8)—were identified almost 20 years ago, although few studies have moved beyond their roles as receptors for the anthrax toxins to address their physiological functions. In the last few years, insight into their endogenous roles has come from two rare diseases: hyaline fibromatosis syndrome, caused by mutations in CMG2, and growth retardation, alopecia, pseudo-anodontia, and optic atrophy (GAPO) syndrome, caused by loss-of-function mutations in TEM8. Although CMG2 and TEM8 are highly homologous at the protein level, the difference in disease symptoms points to variations in the physiological roles of the two anthrax receptors. Here, we focus on the similarities between these receptors in their ability to regulate extracellular matrix homeostasis, angiogenesis, cell migration, and skin elasticity. In this way, we shed light on how mutations in these two related proteins cause such seemingly different diseases and we highlight the existing knowledge gaps that could form the focus of future studies.

scholarly journals Loss-of-Function Mutations in the PRPS1 Gene Cause a Type of Nonsyndromic X-linked Sensorineural Deafness, DFN2

2010 ◽  
Vol 86 (1) ◽  
pp. 65-71 ◽  
Author(s):  
Xuezhong Liu ◽  
Dongyi Han ◽  
Jianzhong Li ◽  
Bing Han ◽  
Xiaomei Ouyang ◽  
...  
Keyword(s):  
Sensorineural Deafness ◽  
Loss Of Function

scholarly journals Membrane protein MHZ3 stabilizes OsEIN2 in rice by interacting with its Nramp-like domain

2018 ◽  
Vol 115 (10) ◽  
pp. 2520-2525 ◽  
Author(s):  
Biao Ma ◽  
Yang Zhou ◽  
Hui Chen ◽  
Si-Jie He ◽  
Yi-Hua Huang ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Ethylene Signaling ◽  
Loss Of Function ◽  
Wild Type ◽  
Protein Ubiquitination ◽  
Ethylene Response ◽  
Gene And Protein Expression ◽  
Domain Loss ◽  
Ethylene Insensitivity ◽  
Insight Into

The phytohormone ethylene regulates many aspects of plant growth and development. EIN2 is the central regulator of ethylene signaling, and its turnover is crucial for triggering ethylene responses. Here, we identified a stabilizer of OsEIN2 through analysis of the rice ethylene-response mutant mhz3. Loss-of-function mutations lead to ethylene insensitivity in etiolated rice seedlings. MHZ3 encodes a previously uncharacterized membrane protein localized to the endoplasmic reticulum. Ethylene induces MHZ3 gene and protein expression. Genetically, MHZ3 acts at the OsEIN2 level in the signaling pathway. MHZ3 physically interacts with OsEIN2, and both the N- and C-termini of MHZ3 specifically associate with the OsEIN2 Nramp-like domain. Loss of mhz3 function reduces OsEIN2 abundance and attenuates ethylene-induced OsEIN2 accumulation, whereas MHZ3 overexpression elevates the abundance of both wild-type and mutated OsEIN2 proteins, suggesting that MHZ3 is required for proper accumulation of OsEIN2 protein. The association of MHZ3 with the Nramp-like domain is crucial for OsEIN2 accumulation, demonstrating the significance of the OsEIN2 transmembrane domains in ethylene signaling. Moreover, MHZ3 negatively modulates OsEIN2 ubiquitination, protecting OsEIN2 from proteasome-mediated degradation. Together, these results suggest that ethylene-induced MHZ3 stabilizes OsEIN2 likely by binding to its Nramp-like domain and impeding protein ubiquitination to facilitate ethylene signal transduction. Our findings provide insight into the mechanisms of ethylene signaling.

scholarly journals Recent Advances in Understanding the Genetic Architecture of Autism

2020 ◽  
Vol 21 (1) ◽  
pp. 289-304 ◽  
Author(s):  
Caroline M. Dias ◽  
Christopher A. Walsh
Keyword(s):  
Genetic Architecture ◽  
De Novo ◽  
Clinical Care ◽  
Copy Number Variants ◽  
Autism Spectrum ◽  
Loss Of Function ◽  
Single Nucleotide Variants ◽  
Single Nucleotide ◽  
Recent Advances ◽  
Insight Into

Recent advances in understanding the genetic architecture of autism spectrum disorder have allowed for unprecedented insight into its biological underpinnings. New studies have elucidated the contributions of a variety of forms of genetic variation to autism susceptibility. While the roles of de novo copy number variants and single-nucleotide variants—causing loss-of-function or missense changes—have been increasingly recognized and refined, mosaic single-nucleotide variants have been implicated more recently in some cases. Moreover, inherited variants (including common variants) and, more recently, rare recessive inherited variants have come into greater focus. Finally, noncoding variants—both inherited and de novo—have been implicated in the last few years. This work has revealed a convergence of diverse genetic drivers on common biological pathways and has highlighted the ongoing importance of increasing sample size and experimental innovation. Continuing to synthesize these genetic findings with functional and phenotypic evidence and translating these discoveries to clinical care remain considerable challenges for the field.

scholarly journals Rare Loss-of-Function Mutation in Complement Component C3 Provides Insight into Molecular and Pathophysiological Determinants of Complement Activity

2015 ◽  
Vol 194 (7) ◽  
pp. 3305-3316 ◽  
Author(s):  
Georgia Sfyroera ◽  
Daniel Ricklin ◽  
Edimara S. Reis ◽  
Hui Chen ◽  
Emilia L. Wu ◽  
...  
Keyword(s):  
Complement Component ◽  
Loss Of Function ◽  
Complement Activity ◽  
Complement Component C3 ◽  
Insight Into

scholarly journals The Cx26-G45E mutation displays increased hemichannel activity in a mouse model of the lethal form of keratitis-ichthyosis-deafness syndrome

2011 ◽  
Vol 22 (24) ◽  
pp. 4776-4786 ◽  
Author(s):  
Gulistan Mese ◽  
Caterina Sellitto ◽  
Leping Li ◽  
Hong-Zhan Wang ◽  
Virginijus Valiunas ◽  
...  
Keyword(s):  
Animal Model ◽  
Mouse Model ◽  
Transgenic Mouse ◽  
Hair Loss ◽  
Epidermal Differentiation ◽  
Gjb2 Gene ◽  
Loss Of Function ◽  
Nonsyndromic Deafness ◽  
Connexin Hemichannels

Mutations in the GJB2 gene (Cx26) cause deafness in humans. Most are loss-of-function mutations and cause nonsyndromic deafness. Some mutations produce a gain of function and cause syndromic deafness associated with skin disorders, such as keratitis-ichthyosis-deafness syndrome (KIDS). Cx26-G45E is a lethal mutation linked to KIDS that forms constitutively active connexin hemichannels. The pathomechanism(s) by which mutant Cx26 hemichannels perturb normal epidermal cornification are poorly understood. We created an animal model for KIDS by generating an inducible transgenic mouse expressing Cx26-G45E in keratinocytes. Cx26-G45E mice displayed reduced viability, hyperkeratosis, scaling, skin folds, and hair loss. Histopathology included hyperplasia, acanthosis, papillomatosis, increased cell size, and osteal plugging. These abnormalities correlated with human KIDS pathology and were associated with increased hemichannel currents in transgenic keratinocytes. These results confirm the pathogenic nature of the G45E mutation and provide a new model for studying the role of aberrant connexin hemichannels in epidermal differentiation and inherited connexin disorders.

scholarly journals Differentially altered Ca2+ regulation and Ca2+ permeability in Cx26 hemichannels formed by the A40V and G45E mutations that cause keratitis ichthyosis deafness syndrome

2010 ◽  
Vol 136 (1) ◽  
pp. 47-62 ◽  
Author(s):  
Helmuth A. Sánchez ◽  
Gülistan Meşe ◽  
Miduturu Srinivas ◽  
Thomas W. White ◽  
Vytas K. Verselis
Keyword(s):  
Single Channel ◽  
Sensorineural Deafness ◽  
Cell Integrity ◽  
Extracellular Loop ◽  
Amino Terminal ◽  
Cysteine Substitution ◽  
Common Causes ◽  
Excessive Entry ◽  
Underlying Mechanisms ◽  
Pore Lining

Mutations in GJB2, which encodes Cx26, are one of the most common causes of inherited deafness in humans. More than 100 mutations have been identified scattered throughout the Cx26 protein, most of which cause nonsyndromic sensorineural deafness. In a subset of mutations, deafness is accompanied by hyperkeratotic skin disorders, which are typically severe and sometimes fatal. Many of these syndromic deafness mutations localize to the amino-terminal and first extracellular loop (E1) domains. Here, we examined two such mutations, A40V and G45E, which are positioned near the TM1/E1 boundary and are associated with keratitis ichthyosis deafness (KID) syndrome. Both of these mutants have been reported to form hemichannels that open aberrantly, leading to “leaky” cell membranes. Here, we quantified the Ca2+ sensitivities and examined the biophysical properties of these mutants at macroscopic and single-channel levels. We find that A40V hemichannels show significantly impaired regulation by extracellular Ca2+, increasing the likelihood of aberrant hemichannel opening as previously suggested. However, G45E hemichannels show only modest impairment in regulation by Ca2+ and instead exhibit a substantial increase in permeability to Ca2+. Using cysteine substitution and examination of accessibility to thiol-modifying reagents, we demonstrate that G45, but not A40, is a pore-lining residue. Both mutants function as cell–cell channels. The data suggest that G45E and A40V are hemichannel gain-of-function mutants that produce similar phenotypes, but by different underlying mechanisms. A40V produces leaky hemichannels, whereas G45E provides a route for excessive entry of Ca2+. These aberrant properties, alone or in combination, can severely compromise cell integrity and lead to increased cell death.

scholarly journals A Drosophila natural variation screen identifies NKCC1 as a substrate of NGLY1 deglycosylation and a modifier of NGLY1 deficiency

2020 ◽  
Author(s):  
Dana M. Talsness ◽  
Katie G. Owings ◽  
Emily Coelho ◽  
Gaelle Mercenne ◽  
John M. Pleinis ◽  
...  
Keyword(s):  
Developmental Delay ◽  
Natural Variation ◽  
Evolutionary Rate ◽  
Phenotypic Variability ◽  
Loss Of Function ◽  
Ion Transporter ◽  
Phenotypic Spectrum ◽  
Mouse Cells ◽  
Covariation Analysis ◽  
Insight Into

AbstractN-Glycanase 1 (NGLY1) is a cytoplasmic deglycosylating enzyme. Loss-of-function mutations in the NGLY1 gene cause NGLY1 deficiency, which is characterized by developmental delay, seizures, and a lack of sweat and tears. To model the phenotypic variability observed among patients, we crossed a Drosophila model of NGLY1 deficiency onto a panel of genetically diverse strains. The resulting progeny showed a phenotypic spectrum from 0-100% lethality. Association analysis on the lethality phenotype as well as an evolutionary rate covariation analysis generated lists of modifying genes, providing insight into NGLY1 function and disease. The top association hit was Ncc69 (human NKCC1/2), a conserved ion transporter. Analyses in NGLY1 -/- mouse cells demonstrated that NKCC1 is misglycosylated and has reduced function, making it only the second confirmed NGLY1 enzymatic substrate. The misregulation of this ion transporter may explain the observed defects in secretory epithelium function in NGLY1 deficiency patients.

scholarly journals A Drosophila screen identifies NKCC1 as a modifier of NGLY1 deficiency

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Dana M Talsness ◽  
Katie G Owings ◽  
Emily Coelho ◽  
Gaelle Mercenne ◽  
John M Pleinis ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Evolutionary Rate ◽  
Phenotypic Variability ◽  
Average Molecular Weight ◽  
Loss Of Function ◽  
Ion Transporter ◽  
Phenotypic Spectrum ◽  
Mouse Cells ◽  
Covariation Analysis ◽  
Insight Into

N-Glycanase 1 (NGLY1) is a cytoplasmic deglycosylating enzyme. Loss-of-function mutations in the NGLY1 gene cause NGLY1 deficiency, which is characterized by developmental delay, seizures, and a lack of sweat and tears. To model the phenotypic variability observed among patients, we crossed a Drosophila model of NGLY1 deficiency onto a panel of genetically diverse strains. The resulting progeny showed a phenotypic spectrum from 0 to 100% lethality. Association analysis on the lethality phenotype, as well as an evolutionary rate covariation analysis, generated lists of modifying genes, providing insight into NGLY1 function and disease. The top association hit was Ncc69 (human NKCC1/2), a conserved ion transporter. Analyses in NGLY1-/- mouse cells demonstrated that NKCC1 has an altered average molecular weight and reduced function. The misregulation of this ion transporter may explain the observed defects in secretory epithelium function in NGLY1 deficiency patients.

scholarly journals Genome-wide synthetic lethal CRISPR screen identifies FIS1 as a genetic interactor of ALS-linked C9ORF72

2019 ◽  
Author(s):  
Noori Chai ◽  
Michael S. Haney ◽  
Julien Couthouis ◽  
David W. Morgens ◽  
Alyssa Benjamin ◽  
...  
Keyword(s):  
Genetic Interaction ◽  
Mitochondrial Fission ◽  
Loss Of Function ◽  
Synthetic Lethal ◽  
Genome Wide ◽  
A Genome ◽  
Crispr Screen ◽  
Insight Into ◽  
Mitochondrial Membrane Protein ◽  
Lateral Sclerosis

AbstractMutations in the C9ORF72 gene are the most common cause of amyotrophic lateral sclerosis (ALS). Both toxic gain of function and loss of function pathogenic mechanisms have been proposed. Accruing evidence from mouse knockout studies point to a role for C9ORF72 as a regulator of immune function. To provide further insight into its cellular function, we performed a genome-wide synthetic lethal CRISPR screen in human myeloid cells lacking C9ORF72. We discovered a strong synthetic lethal genetic interaction between C9ORF72 and FIS1, which encodes a mitochondrial membrane protein involved in mitochondrial fission and mitophagy. Mass spectrometry experiments revealed that in C9ORF72 knockout cells, FIS1 strongly bound to a class of immune regulators that activate the receptor for advanced glycation end (RAGE) products and trigger inflammatory cascades. These findings present a novel genetic interactor for C9ORF72 and suggest a compensatory role for FIS1 in suppressing inflammatory signaling in the absence of C9ORF72.

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