scholarly journals Peptide-Based Targeting of the L-Type Calcium Channel Corrects the Loss-of-Function Phenotype of Two Novel Mutations of the CACNA1 Gene Associated With Brugada Syndrome

2021 ◽  
Vol 11 ◽  
Author(s):  
Vittoria Di Mauro ◽  
Paola Ceriotti ◽  
Francesco Lodola ◽  
Nicolò Salvarani ◽  
Jessica Modica ◽  
...  
Keyword(s):  
Calcium Channel ◽  
Brugada Syndrome ◽  
Half Life ◽  
Specific Treatment ◽  
Pharmacological Therapy ◽  
Cardiac Cells ◽  
Hek293 Cells ◽  
Loss Of Function ◽  
Gene Encoding ◽  
Protein Levels

Brugada syndrome (BrS) is an inherited arrhythmogenic disease that may lead to sudden cardiac death in young adults with structurally normal hearts. No pharmacological therapy is available for BrS patients. This situation highlights the urgent need to overcome current difficulties by developing novel groundbreaking curative strategies. BrS has been associated with mutations in 18 different genes of which loss-of-function (LoF) CACNA1C mutations constitute the second most common cause. Here we tested the hypothesis that BrS associated with mutations in the CACNA1C gene encoding the L-type calcium channel (LTCC) pore-forming unit (Cavα1.2) is functionally reverted by administration of a mimetic peptide (MP), which through binding to the LTCC chaperone beta subunit (Cavβ2) restores the physiological life cycle of aberrant LTCCs. Two novel Cavα1.2 mutations associated with BrS were identified in young individuals. Transient transfection in heterologous and cardiac cells showed LoF phenotypes with reduced Ca2+ current (ICa). In HEK293 cells overexpressing the two novel Cavα1.2 mutations, Western blot analysis and cell surface biotinylation assays revealed reduced Cavα1.2 protein levels at the plasma membrane for both mutants. Nano-BRET, Nano-Luciferase assays, and confocal microscopy analyses showed (i) reduced affinity of Cavα1.2 for its Cavβ2 chaperone, (ii) shortened Cavα1.2 half-life in the membrane, and (iii) impaired subcellular localization. Treatment of Cavα1.2 mutant-transfected cells with a cell permeant MP restored channel trafficking and physiologic channel half-life, thereby resulting in ICa similar to wild type. These results represent the first step towards the development of a gene-specific treatment for BrS due to defective trafficking of mutant LTCC.

scholarly journals Subclinical Inflammatory Status in Rett Syndrome

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Alessio Cortelazzo ◽  
Claudio De Felice ◽  
Roberto Guerranti ◽  
Cinzia Signorini ◽  
Silvia Leoncini ◽  
...  
Keyword(s):  
Gene Mutation ◽  
Rett Syndrome ◽  
De Novo ◽  
Clinical Chemistry ◽  
Neurodevelopmental Disorder ◽  
Loss Of Function ◽  
Gene Encoding ◽  
Protein Levels ◽  
Large Deletions ◽  
Inflammatory Status

Inflammation has been advocated as a possible common central mechanism for developmental cognitive impairment. Rett syndrome (RTT) is a devastating neurodevelopmental disorder, mainly caused byde novoloss-of-function mutations in the gene encoding MeCP2. Here, we investigated plasma acute phase response (APR) in stage II (i.e., “pseudo-autistic”) RTT patients by routine haematology/clinical chemistry and proteomic 2-DE/MALDI-TOF analyses as a function of four majorMECP2gene mutation types (R306C, T158M, R168X, and large deletions). Elevated erythrocyte sedimentation rate values (median 33.0 mm/h versus 8.0 mm/h,P<0.0001) were detectable in RTT, whereas C-reactive protein levels were unchanged (P=0.63). The 2-DE analysis identified significant changes for a total of 17 proteins, the majority of which were categorized as APR proteins, either positive (n=6spots) or negative (n=9spots), and to a lesser extent as proteins involved in the immune system (n=2spots), with some proteins having overlapping functions on metabolism (n=7spots). The number of protein changes was proportional to the severity of the mutation. Our findings reveal for the first time the presence of a subclinical chronic inflammatory status related to the “pseudo-autistic” phase of RTT, which is related to the severity carried by theMECP2gene mutation.

Abstract 4413: Accelerated Inactivation of the L-type Calcium due to a Mutation in CACNB2b Underlies the Development of a Brugada ECG Phenotype

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Jonathan M Cordeiro ◽  
Mark Marieb ◽  
Ryan Pfeiffer ◽  
Kirstine Calloe ◽  
Elena Burashnikov ◽  
...  
Keyword(s):  
Action Potential ◽  
Calcium Channel ◽  
Brugada Syndrome ◽  
Vasovagal Syncope ◽  
Total Charge ◽  
Loss Of Function ◽  
St Segment Elevation ◽  
St Segment ◽  
Steady State Inactivation ◽  
The Right

Background: Ion channelopathies are responsible for a number of genetic cardiac arrhythmia syndromes. Recent work demonstrated an association between mutations in CACNA1c and CACNB2b, the genes that encode the α and β subunits of the L-type calcium channel, and the Brugada syndrome (BrS). The mutations previously described all caused a loss of function secondary to a major reduction in peak calcium channel current (I Ca ). In the present study we describe a novel CACNB2b mutation associated with BrS in which loss of function was caused by accelerated inactivation of I Ca . Methods and Results: The proband, a 32 yo male, displayed a saddleback ST segment elevation in the right precordial leads that converted to a coved-type ECG following a procainamide challenge. His EP study was positive with double extrastimuli inducing polymorphic VT/VF. He was also diagnosed with vasovagal syncope. Genomic DNA was isolated from blood lymphocytes. All exons and intron borders of 12 ion channel genes were amplified and sequenced. The only mutation uncovered was a missense mutation (T11I) in CACNB2b. The effect of this mutation was studied by expression of WT or T11I CACNB2b in TSA201 cells co-transfected with WT CANCA1c and CACNA2d. Patch clamp analysis showed no difference in I Ca density between WT and T11I (17.9±1.8 vs 22.5±4.3 pA/pF, respectively at +20mV). Similarly, steady-state inactivation and channel recovery was not different between WT and T11I mutant channels. However, both the fast and slow decay of I Ca produced by T11I mutant were significantly faster compared to WT at potentials between −10 to +30 mV, suggesting a reduction in depolarizing current during the course of an action potential. Application of action potential voltage clamp pulses confirmed that T11I total charge was reduced by 42±2.3% compared to WT (p<0.05). Conclusion: We report the first Brugada syndrome mutation in CaCNB2b resulting in accelerated inactivation of the L-type calcium channel. The T11I mutation caused a faster decay of cardiac L-type calcium current but did not significantly alter the magnitude of the peak current. Our results suggest that a reduced total charge carried by I Ca during the plateau of the action potential predisposes to the Brugada phenotype.

scholarly journals Novel SCN9A missense mutations contribute to congenital insensitivity to pain: Unexpected correlation between electrophysiological characterization and clinical phenotype

2020 ◽  
Vol 16 ◽  
pp. 174480692092388
Author(s):  
Jiaoli Sun ◽  
Lulu Li ◽  
Luyao Yang ◽  
Guangyou Duan ◽  
Tingbin Ma ◽  
...  
Keyword(s):  
Sodium Current ◽  
Hek293 Cells ◽  
Pain Patient ◽  
Missense Mutations ◽  
Loss Of Function ◽  
Protein Levels ◽  
Congenital Insensitivity ◽  
Congenital Insensitivity To Pain ◽  
Electrophysiological Characterization ◽  
Insensitivity To Pain

Congenital insensitivity to pain (OMIM 243000) is an extremely rare disorder caused by loss-of-function mutations in SCN9A encoding Nav1.7. Although the SCN9A mutations and phenotypes of painlessness and anosmia/hyposmia in patients are previously well documented, the complex relationship between genotype and phenotype of congenital insensitivity to pain remains unclear. Here, we report a congenital insensitivity to pain patient with novel SCN9A mutations. Functional significance of novel SCN9A mutations was assessed in HEK293 cells expressing Nav1.7, the results showed that p.Arg99His significantly decreased current density and reduced total Nav1.7 protein levels, whereas p.Trp917Gly almost abolished Nav1.7 sodium current without affecting its protein expression. These revealed that mutations in Nav1.7 in this congenital insensitivity to pain patient still retained partial channel function, but the patient showed completely painlessness, the unexpected genotypic-phenotypic relationship of SCN9A mutations in our patient may challenge the previous findings “Nav1.7 total loss-of-function leads to painlessness.” Additionally, these findings are helpful for understanding the critical amino acid for maintaining function of Nav1.7, thus contributing to the development of Nav1.7-targeted analgesics.

scholarly journals LOXL1 confers antiapoptosis and promotes gliomagenesis through stabilizing BAG2

2020 ◽  
Vol 27 (11) ◽  
pp. 3021-3036 ◽  
Author(s):  
Hua Yu ◽  
Jun Ding ◽  
Hongwen Zhu ◽  
Yao Jing ◽  
Hu Zhou ◽  
...  
Keyword(s):  
Molecular Chaperone ◽  
Glioma Cell ◽  
Lysyl Oxidase ◽  
The Cancer Genome Atlas ◽  
Loss Of Function ◽  
Protein Levels ◽  
Important Mediator ◽  
Cancer Genome Atlas ◽  
Potential Strategy ◽  
Glioma Progression

Abstract The lysyl oxidase (LOX) family is closely related to the progression of glioma. To ensure the clinical significance of LOX family in glioma, The Cancer Genome Atlas (TCGA) database was mined and the analysis indicated that higher LOXL1 expression was correlated with more malignant glioma progression. The functions of LOXL1 in promoting glioma cell survival and inhibiting apoptosis were studied by gain- and loss-of-function experiments in cells and animals. LOXL1 was found to exhibit antiapoptotic activity by interacting with multiple antiapoptosis modulators, especially BAG family molecular chaperone regulator 2 (BAG2). LOXL1-D515 interacted with BAG2-K186 through a hydrogen bond, and its lysyl oxidase activity prevented BAG2 degradation by competing with K186 ubiquitylation. Then, we discovered that LOXL1 expression was specifically upregulated through the VEGFR-Src-CEBPA axis. Clinically, the patients with higher LOXL1 levels in their blood had much more abundant BAG2 protein levels in glioma tissues. Conclusively, LOXL1 functions as an important mediator that increases the antiapoptotic capacity of tumor cells, and approaches targeting LOXL1 represent a potential strategy for treating glioma. In addition, blood LOXL1 levels can be used as a biomarker to monitor glioma progression.

scholarly journals Gain-of-function GABRB3 variants identified in vigabatrin-hypersensitive epileptic encephalopathies

2020 ◽  
Vol 2 (2) ◽  
Author(s):  
Nathan L Absalom ◽  
Vivian W Y Liao ◽  
Kavitha Kothur ◽  
Dinesh C Indurthi ◽  
Bruce Bennetts ◽  
...  
Keyword(s):  
De Novo ◽  
Drug Effects ◽  
Receptor Expression ◽  
Aminobutyric Acid ◽  
Loss Of Function ◽  
Molecular Phenotype ◽  
Gain Of Function ◽  
Gene Encoding ◽  
Epileptic Encephalopathies ◽  
Receptor Phenotype

Abstract Variants in the GABRB3 gene encoding the β3-subunit of the γ-aminobutyric acid type A ( receptor are associated with various developmental and epileptic encephalopathies. Typically, these variants cause a loss-of-function molecular phenotype whereby γ-aminobutyric acid has reduced inhibitory effectiveness leading to seizures. Drugs that potentiate inhibitory GABAergic activity, such as nitrazepam, phenobarbital or vigabatrin, are expected to compensate for this and thereby reduce seizure frequency. However, vigabatrin, a drug that inhibits γ-aminobutyric acid transaminase to increase tonic γ-aminobutyric acid currents, has mixed success in treating seizures in patients with GABRB3 variants: some patients experience seizure cessation, but there is hypersensitivity in some patients associated with hypotonia, sedation and respiratory suppression. A GABRB3 variant that responds well to vigabatrin involves a truncation variant (p.Arg194*) resulting in a clear loss-of-function. We hypothesized that patients with a hypersensitive response to vigabatrin may exhibit a different γ-aminobutyric acid A receptor phenotype. To test this hypothesis, we evaluated the phenotype of de novo variants in GABRB3 (p.Glu77Lys and p.Thr287Ile) associated with patients who are clinically hypersensitive to vigabatrin. We introduced the GABRB3 p.Glu77Lys and p.Thr287Ile variants into a concatenated synaptic and extrasynaptic γ-aminobutyric acid A receptor construct, to resemble the γ-aminobutyric acid A receptor expression by a patient heterozygous for the GABRB3 variant. The mRNA of these constructs was injected into Xenopus oocytes and activation properties of each receptor measured by two-electrode voltage clamp electrophysiology. Results showed an atypical gain-of-function molecular phenotype in the GABRB3 p.Glu77Lys and p.Thr287Ile variants characterized by increased potency of γ-aminobutyric acid A without change to the estimated maximum open channel probability, deactivation kinetics or absolute currents. Modelling of the activation properties of the receptors indicated that either variant caused increased chloride flux in response to low concentrations of γ-aminobutyric acid that mediate tonic currents. We therefore propose that the hypersensitivity reaction to vigabatrin is a result of GABRB3 variants that exacerbate GABAergic tonic currents and caution is required when prescribing vigabatrin. In contrast, drug strategies increasing tonic currents in loss-of-function variants are likely to be a safe and effective therapy. This study demonstrates that functional genomics can explain beneficial and adverse anti-epileptic drug effects, and propose that vigabatrin should be considered in patients with clear loss-of-function GABRB3 variants.

scholarly journals TRIM27 interacts with Iκbα to promote the growth of human renal cancer cells through regulating the NF-κB pathway

BMC Cancer ◽  
2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Chengwu Xiao ◽  
Wei Zhang ◽  
Meimian Hua ◽  
Huan Chen ◽  
Bin Yang ◽  
...  
Keyword(s):  
Cell Lines ◽  
Prognostic Indicator ◽  
The Cancer Genome Atlas ◽  
Mrna Levels ◽  
Loss Of Function ◽  
Protein Levels ◽  
Kaplan Meier ◽  
Cancer Genome Atlas

Abstract Background The tripartite motif (TRIM) family proteins exhibit oncogenic roles in various cancers. The roles of TRIM27, a member of the TRIM super family, in renal cell carcinoma (RCC) remained unexplored. In the current study, we aimed to investigate the clinical impact and roles of TRIM27 in the development of RCC. Methods The mRNA levels of TRIM27 and Kaplan–Meier survival of RCC were analyzed from The Cancer Genome Atlas database. Real-time PCR and Western blotting were used to measure the mRNA and protein levels of TRIM27 both in vivo and in vitro. siRNA and TRIM27 were exogenously overexpressed in RCC cell lines to manipulate TRIM27 expression. Results We discovered that TRIM27 was elevated in RCC patients, and the expression of TRIM27 was closely correlated with poor prognosis. The loss of function and gain of function results illustrated that TRIM27 promotes cell proliferation and inhibits apoptosis in RCC cell lines. Furthermore, TRIM27 expression was positively associated with NF-κB expression in patients with RCC. Blocking the activity of NF-κB attenuated the TRIM27-mediated enhancement of proliferation and inhibition of apoptosis. TRIM27 directly interacted with Iκbα, an inhibitor of NF-κB, to promote its ubiquitination, and the inhibitory effects of TRIM27 on Iκbα led to NF-κB activation. Conclusions Our results suggest that TRIM27 exhibits an oncogenic role in RCC by regulating NF-κB signaling. TRIM27 serves as a specific prognostic indicator for RCC, and strategies targeting the suppression of TRIM27 function may shed light on future therapeutic approaches.

scholarly journals The Novel ALG-2 Target Protein CDIP1 Promotes Cell Death by Interacting with ESCRT-I and VAPA/B

2021 ◽  
Vol 22 (3) ◽  
pp. 1175
Author(s):  
Ryuta Inukai ◽  
Kanako Mori ◽  
Keiko Kuwata ◽  
Chihiro Suzuki ◽  
Masatoshi Maki ◽  
...  
Keyword(s):  
Cell Death ◽  
Essential Gene ◽  
Susceptibility Gene ◽  
Target Protein ◽  
Hek293 Cells ◽  
Dependent Manner ◽  
Gene Encoding ◽  
Endosomal Sorting ◽  
Cell Death Pathways ◽  
Apoptotic Protein

Apoptosis-linked gene 2 (ALG-2, also known as PDCD6) is a member of the penta-EF-hand (PEF) family of Ca2+-binding proteins. The murine gene encoding ALG-2 was originally reported to be an essential gene for apoptosis. However, the role of ALG-2 in cell death pathways has remained elusive. In the present study, we found that cell death-inducing p53 target protein 1 (CDIP1), a pro-apoptotic protein, interacts with ALG-2 in a Ca2+-dependent manner. Co-immunoprecipitation analysis of GFP-fused CDIP1 (GFP-CDIP1) revealed that GFP-CDIP1 associates with tumor susceptibility gene 101 (TSG101), a known target of ALG-2 and a subunit of endosomal sorting complex required for transport-I (ESCRT-I). ESCRT-I is a heterotetrameric complex composed of TSG101, VPS28, VPS37 and MVB12/UBAP1. Of diverse ESCRT-I species originating from four VPS37 isoforms (A, B, C, and D), CDIP1 preferentially associates with ESCRT-I containing VPS37B or VPS37C in part through the adaptor function of ALG-2. Overexpression of GFP-CDIP1 in HEK293 cells caused caspase-3/7-mediated cell death. In addition, the cell death was enhanced by co-expression of ALG-2 and ESCRT-I, indicating that ALG-2 likely promotes CDIP1-induced cell death by promoting the association between CDIP1 and ESCRT-I. We also found that CDIP1 binds to vesicle-associated membrane protein-associated protein (VAP)A and VAPB through the two phenylalanines in an acidic tract (FFAT)-like motif in the C-terminal region of CDIP1, mutations of which resulted in reduction of CDIP1-induced cell death. Therefore, our findings suggest that different expression levels of ALG-2, ESCRT-I subunits, VAPA and VAPB may have an impact on sensitivity of anticancer drugs associated with CDIP1 expression.

scholarly journals The Multifaceted Roles of MicroRNAs in Cystic Fibrosis

Diagnostics ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1102
Author(s):  
Fatima Domenica Elisa De Palma ◽  
Valeria Raia ◽  
Guido Kroemer ◽  
Maria Chiara Maiuri
Keyword(s):  
Cystic Fibrosis ◽  
Respiratory Infections ◽  
Current Knowledge ◽  
Pancreatic Insufficiency ◽  
Clinical Manifestations ◽  
Predictive Biomarkers ◽  
Loss Of Function ◽  
Gene Encoding ◽  
Multisystemic Disease

Cystic fibrosis (CF) is a lifelong disorder affecting 1 in 3500 live births worldwide. It is a monogenetic autosomal recessive disease caused by loss-of-function mutations in the gene encoding the chloride channel cystic fibrosis transmembrane conductance regulator (CFTR), the impairment of which leads to ionic disequilibria in exocrine organs. This translates into a chronic multisystemic disease characterized by airway obstruction, respiratory infections, and pancreatic insufficiency as well as hepatobiliary and gastrointestinal dysfunction. Molecular characterization of the mutational heterogeneity of CFTR (affected by more than 2000 variants) improved the understanding and management of CF. However, these CFTR variants are linked to different clinical manifestations and phenotypes, and they affect response to treatments. Expanding evidence suggests that multisystemic disease affects CF pathology via impairing either CFTR or proteins regulated by CFTR. Thus, altering the expression of miRNAs in vivo could constitute an appealing strategy for developing new CF therapies. In this review, we will first describe the pathophysiology and clinical management of CF. Then, we will summarize the current knowledge on altered miRNAs in CF patients, with a focus on the miRNAs involved in the deregulation of CFTR and in the modulation of inflammation. We will highlight recent findings on the potential utility of measuring circulating miRNAs in CF as diagnostic, prognostic, and predictive biomarkers. Finally, we will provide an overview on potential miRNA-based therapeutic approaches.

scholarly journals Genomic Variation in IbA10G2 and Other Patient-Derived Cryptosporidium hominis Subtypes

2016 ◽  
Vol 55 (3) ◽  
pp. 844-858 ◽  
Author(s):  
Per Sikora ◽  
Sofia Andersson ◽  
Jadwiga Winiecka-Krusnell ◽  
Björn Hallström ◽  
Cecilia Alsmark ◽  
...  
Keyword(s):  
Parasite Burden ◽  
Genomic Variation ◽  
Loss Of Function ◽  
Oocyst Wall ◽  
Gene Encoding ◽  
Cryptosporidium Hominis ◽  
Content Type ◽  
Successful Isolation ◽  
Target Dna ◽  
Stool Samples

ABSTRACTIn order to improve genotyping and epidemiological analysis ofCryptosporidiumspp., genomic data need to be generated directly from a broad range of clinical specimens. Utilizing a robust method that we developed for the purification and generation of amplified target DNA, we present its application for the successful isolation and whole-genome sequencing of 14 differentCryptosporidium hominispatient specimens. Six isolates of subtype IbA10G2 were analyzed together with a single representative each of 8 other subtypes: IaA20R3, IaA23R3, IbA9G3, IbA13G3, IdA14, IeA11G3T3, IfA12G1, and IkA18G1. Parasite burden was measured over a range of more than 2 orders of magnitude for all samples, while the genomes were sequenced to mean depths of between 17× and 490× coverage. Sequence homology-based functional annotation identified several genes of interest, including the gene encodingCryptosporidiumoocyst wall protein 9 (COWP9), which presented a predicted loss-of-function mutation in all the sequence subtypes, except for that seen with IbA10G2, which has a sequence identical to theCryptosporidium parvumreference Iowa II sequence. Furthermore, phylogenetic analysis showed that all the IbA10G2 genomes form a monophyletic clade in theC. hoministree as expected and yet display some heterogeneity within the IbA10G2 subtype. The current report validates the aforementioned method for isolating and sequencingCryptosporidiumdirectly from clinical stool samples. In addition, the analysis demonstrates the potential in mining data generated from sequencing multiple whole genomes ofCryptosporidiumfrom human fecal samples, while alluding to the potential for a higher degree of genotyping withinCryptosporidiumepidemiology.

Sign in / Sign up

Export Citation Format

Share Document