scholarly journals αIIbβ3 variants in ten families with autosomal dominant macrothrombocytopenia: Expanding the mutational and clinical spectrum

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0235136
Author(s):  
Sara Morais ◽  
Jorge Oliveira ◽  
Catarina Lau ◽  
Mónica Pereira ◽  
Marta Gonçalves ◽  
...  
Keyword(s):  
Binding Sites ◽  
Autosomal Dominant ◽  
Transmembrane Domain ◽  
Laboratory Data ◽  
Atp Release ◽  
Cytoplasmic Domains ◽  
Pathogenic Variants ◽  
Distinct Disease ◽  
And Function ◽  
First Time

Background Rare pathogenic variants in either the ITGA2B or ITGB3 genes have been linked to autosomal dominant macrothrombocytopenia associated with abnormal platelet production and function, deserving the designation of Glanzmann Thrombasthenia-Like Syndrome (GTLS) or ITGA2B/ITGB3-related thrombocytopenia. Objectives To describe a series of patients with familial macrothrombocytopenia and decreased expression of αIIbβ3 integrin due to defects in the ITGA2B or ITGB3 genes. Methods We reviewed the clinical and laboratory records of 10 Portuguese families with GTLS (33 patients and 11 unaffected relatives), including the functional and genetic defects. Results Patients had absent to moderate bleeding, macrothrombocytopenia, low αIIbβ3 expression, impaired platelet aggregation/ATP release to physiological agonists and low expression of activation-induced binding sites on αIIbβ3 (PAC-1) and receptor-induced binding sites on its ligand (bound fibrinogen), upon stimulation with TRAP-6 and ADP. Evidence for constitutive αIIbβ3 activation, occurred in 2 out of 9 patients from 8 families studied, but also in 2 out of 12 healthy controls. We identified 7 missense variants: 3 in ITGA2B (5 families), and 4 in ITGB3 (5 families). Three variants (αIIb: p.Arg1026Trp and p.Arg1026Gln and β3: p.Asp749His) were previously reported. The remaining (αIIb: p.Gly1007Val and β3: p.Thr746Pro, p.His748Pro and p.Arg760Cys) are new, expanding the αIIbβ3 defects associated with GTLS. The integration of the clinical and laboratory data allowed the identification of two GTLS subgroups, with distinct disease severity. Conclusions Previously reported ITGA2B and ITGB3 variants related to thrombocytopenia were clustered in a confined region of the membrane-proximal cytoplasmic domains, the inner membrane clasp. For the first time, variants are reported at the outer membrane clasp, at the transmembrane domain of αIIb, and at the membrane distal cytoplasmic domains of β3. This is the largest single-center series of inherited macrothrombocytopenia associated with αIIbβ3 variants published to date.

scholarly journals Further confirmation of the association of SLC12A2 with non-syndromic autosomal-dominant hearing impairment

2021 ◽  
Author(s):  
Samuel M. Adadey ◽  
Isabelle Schrauwen ◽  
Elvis Twumasi Aboagye ◽  
Thashi Bharadwaj ◽  
Kevin K. Esoh ◽  
...  
Keyword(s):  
Inner Ear ◽  
Hearing Impairment ◽  
Molecular Mechanisms ◽  
Autosomal Dominant ◽  
Genetic Diagnosis ◽  
Current Data ◽  
Pathogenic Variants ◽  
Alternatively Spliced ◽  
Sub Saharan ◽  
And Function

AbstractCongenital hearing impairment (HI) is genetically heterogeneous making its genetic diagnosis challenging. Investigation of novel HI genes and variants will enhance our understanding of the molecular mechanisms and to aid genetic diagnosis. We performed exome sequencing and analysis using DNA samples from affected members of two large families from Ghana and Pakistan, segregating autosomal-dominant (AD) non-syndromic HI (NSHI). Using in silico approaches, we modeled and evaluated the effect of the likely pathogenic variants on protein structure and function. We identified two likely pathogenic variants in SLC12A2, c.2935G>A:p.(E979K) and c.2939A>T:p.(E980V), which segregate with NSHI in a Ghanaian and Pakistani family, respectively. SLC12A2 encodes an ion transporter crucial in the homeostasis of the inner ear endolymph and has recently been reported to be implicated in syndromic and non-syndromic HI. Both variants were mapped to alternatively spliced exon 21 of the SLC12A2 gene. Exon 21 encodes for 17 residues in the cytoplasmatic tail of SLC12A2, is highly conserved between species, and preferentially expressed in cochlear tissues. A review of previous studies and our current data showed that out of ten families with either AD non-syndromic or syndromic HI, eight (80%) had variants within the 17 amino acid residue region of exon 21 (48 bp), suggesting that this alternate domain is critical to the transporter activity in the inner ear. The genotypic spectrum of SLC12A2 was expanded and the involvement of SLC12A2 in ADNSHI was confirmed. These results also demonstrate the role that SLC12A2 plays in ADNSHI in diverse populations including sub-Saharan Africans.

scholarly journals Acetylcholine Receptor Gating at Extracellular Transmembrane Domain Interface: the Cys-Loop and M2–M3 Linker

2007 ◽  
Vol 130 (6) ◽  
pp. 547-558 ◽  
Author(s):  
Archana Jha ◽  
David J. Cadugan ◽  
Prasad Purohit ◽  
Anthony Auerbach
Keyword(s):  
Acetylcholine Receptor ◽  
Binding Sites ◽  
Transmembrane Domain ◽  
Relative Timing ◽  
Α Subunit ◽  
Value Analysis ◽  
And Function ◽  
Pore Lining ◽  
Acetylcholine Receptor Channel ◽  
Receptor Channel

Acetylcholine receptor channel gating is a propagated conformational cascade that links changes in structure and function at the transmitter binding sites in the extracellular domain (ECD) with those at a “gate” in the transmembrane domain (TMD). We used Φ-value analysis to probe the relative timing of the gating motions of α-subunit residues located near the ECD–TMD interface. Mutation of four of the seven amino acids in the M2–M3 linker (which connects the pore-lining M2 helix with the M3 helix), including three of the four residues in the core of the linker, changed the diliganded gating equilibrium constant (Keq) by up to 10,000-fold (P272 > I274 > A270 > G275). The average Φ-value for the whole linker was ∼0.64. One interpretation of this result is that the gating motions of the M2–M3 linker are approximately synchronous with those of much of M2 (∼0.64), but occur after those of the transmitter binding site region (∼0.93) and loops 2 and 7 (∼0.77). We also examined mutants of six cys-loop residues (V132, T133, H134, F135, P136, and F137). Mutation of V132, H134, and F135 changed Keq by 2800-, 10-, and 18-fold, respectively, and with an average Φ-value of 0.74, similar to those of other cys-loop residues. Even though V132 and I274 are close, the energetic coupling between I and V mutants of these positions was small (≤0.51 kcal mol−1). The M2–M3 linker appears to be the key moving part that couples gating motions at the base of the ECD with those in TMD. These interactions are distributed along an ∼16-Å border and involve about a dozen residues.

scholarly journals Structure and Function of the ABCD1 Variant Database: 20 Years, 940 Pathogenic Variants, and 3400 Cases of Adrenoleukodystrophy

Cells ◽  
2022 ◽  
Vol 11 (2) ◽  
pp. 283
Author(s):  
Eric J. Mallack ◽  
Kerry Gao ◽  
Marc Engelen ◽  
Stephan Kemp
Keyword(s):  
Transmembrane Domain ◽  
Missense Variant ◽  
Pathogenic Variant ◽  
Atp Binding ◽  
Pathogenic Variants ◽  
Mutation Database ◽  
Variant Frequency ◽  
Additional Level ◽  
And Function ◽  
Variant Database

The progressive neurometabolic disorder X-linked adrenoleukodystrophy (ALD) is caused by pathogenic variants in the ABCD1 gene, which encodes the peroxisomal ATP-binding transporter for very-long-chain fatty acids. The clinical spectrum of ALD includes adrenal insufficiency, myelopathy, and/or leukodystrophy. A complicating factor in disease management is the absence of a genotype–phenotype correlation in ALD. Since 1999, most ABCD1 (likely) pathogenic and benign variants have been reported in the ABCD1 Variant Database. In 2017, following the expansion of ALD newborn screening, the database was rebuilt. To add an additional level of confidence with respect to pathogenicity, for each variant, it now also reports the number of cases identified and, where available, experimental data supporting the pathogenicity of the variant. The website also provides information on a number of ALD-related topics in several languages. Here, we provide an updated analysis of the known variants in ABCD1. The order of pathogenic variant frequency, overall clustering of disease-causing variants in exons 1–2 (transmembrane domain spanning region) and 6–9 (ATP-binding domain), and the most commonly reported pathogenic variant p.Gln472Argfs*83 in exon 5 are consistent with the initial reports of the mutation database. Novel insights include nonrandom clustering of high-density missense variant hotspots within exons 1, 2, 6, 8, and 9. Perhaps more importantly, we illustrate the importance of collaboration and utility of the database as a scientific, clinical, and ALD-community-wide resource.

scholarly journals Differential lipid binding of vinculin isoforms promotes quasi-equivalent dimerization

2016 ◽  
Vol 113 (34) ◽  
pp. 9539-9544 ◽  
Author(s):  
Krishna Chinthalapudi ◽  
Erumbi S. Rangarajan ◽  
David T. Brown ◽  
Tina Izard
Keyword(s):  
Cardiac Failure ◽  
Binding Sites ◽  
Autosomal Dominant ◽  
Cell Function ◽  
Lipid Binding ◽  
Wild Type ◽  
Adhesion Sites ◽  
Intercalated Discs ◽  
Alternatively Spliced ◽  
And Function

The main cause of death globally remains debilitating heart conditions, such as dilated cardiomyopathy (DCM) and hypertrophic cardiomyopathy (HCM), which are often due to mutations of specific components of adhesion complexes. Vinculin regulates these complexes and plays essential roles in intercalated discs that are necessary for muscle cell function and coordinated movement and in the development and function of the heart. Humans bearing familial or sporadic mutations in vinculin suffer from chronic, progressively debilitating DCM that ultimately leads to cardiac failure and death, whereas autosomal dominant mutations in vinculin can also provoke HCM, causing acute cardiac failure. The DCM/HCM-associated mutants of vinculin occur in the 68-residue insert unique to the muscle-specific, alternatively spliced isoform of vinculin, termed metavinculin (MV). Contrary to studies that suggested that phosphoinositol-4,5-bisphosphate (PIP2) only induces vinculin homodimers, which are asymmetric, we show that phospholipid binding results in a domain-swapped symmetric MV dimer via a quasi-equivalent interface compared with vinculin involving R975. Although one of the two PIP2 binding sites is preserved, the symmetric MV dimer that bridges two PIP2 molecules differs from the asymmetric vinculin dimer that bridges only one PIP2. Unlike vinculin, wild-type MV and the DCM/HCM-associated R975W mutant bind PIP2 in their inactive conformations, and R975W MV fails to dimerize. Mutating selective vinculin residues to their corresponding MV residues, or vice versa, switches the isoform’s dimeric constellation and lipid binding site. Collectively, our data suggest that MV homodimerization modulates microfilament attachment at muscular adhesion sites and furthers our understanding of MV-mediated cardiac remodeling.

Conformation of Ribosomes from Escherichia Coli

1974 ◽  
Vol 32 ◽  
pp. 210-211
Author(s):  
M. Boublik ◽  
W. Hellmann ◽  
F. Jenkins
Keyword(s):  
Binding Sites ◽  
Ribosomal Proteins ◽  
Fluorescent Dyes ◽  
Protein Biosynthesis ◽  
Three Dimensional ◽  
Spatial Arrangement ◽  
Dimensional Structure ◽  
Complete Understanding ◽  
And Function

The present knowledge of the three-dimensional structure of ribosomes is far too limited to enable a complete understanding of the various roles which ribosomes play in protein biosynthesis. The spatial arrangement of proteins and ribonuclec acids in ribosomes can be analysed in many ways. Determination of binding sites for individual proteins on ribonuclec acid and locations of the mutual positions of proteins on the ribosome using labeling with fluorescent dyes, cross-linking reagents, neutron-diffraction or antibodies against ribosomal proteins seem to be most successful approaches. Structure and function of ribosomes can be correlated be depleting the complete ribosomes of some proteins to the functionally inactive core and by subsequent partial reconstitution in order to regain active ribosomal particles.

Strategies for Oral Delivery of Metal-Saturated Lactoferrin

2019 ◽  
Vol 20 (11) ◽  
pp. 1046-1051 ◽  
Author(s):  
Przemysław Gajda-Morszewski ◽  
Klaudyna Śpiewak-Wojtyła ◽  
Maria Oszajca ◽  
Małgorzata Brindell
Keyword(s):  
Biological Activity ◽  
Oral Delivery ◽  
Therapeutic Potential ◽  
Structure And Function ◽  
The Difference ◽  
And Function ◽  
First Time

Lactoferrin was isolated and purified for the first time over 50-years ago. Since then, extensive studies on the structure and function of this protein have been performed and the research is still being continued. In this mini-review we focus on presenting recent scientific efforts towards the elucidation of the role and therapeutic potential of lactoferrin saturated with iron(III) or manganese(III) ions. The difference in biological activity of metal-saturated lactoferrin vs. the unmetalated one is emphasized. The strategies for oral delivery of lactoferrin, are also reviewed, with particular attention to the metalated protein.

Redox Potential - (Electronic) Structure Relationships in 18- and 17-Electron Mononitrile (or Monocarbonyl) Diphosphine Complexes of Re and Fe

2001 ◽  
Vol 66 (1) ◽  
pp. 139-154 ◽  
Author(s):  
M. Fátima C. Guedes Da Silva ◽  
Luísa M. D. R. S. Martins ◽  
João J. R. Fraústo Da Silva ◽  
Armando J. L. Pombeiro
Keyword(s):  
Cyclic Voltammetry ◽  
Electronic Structure ◽  
Binding Sites ◽  
Closed Shell ◽  
Carbonyl Complexes ◽  
Metal Centre ◽  
Pt Electrode ◽  
Metal Site ◽  
Oxidation Potentials ◽  
First Time

The organonitrile or carbonyl complexes cis-[ReCl(RCN)(dppe)2] (1) (R = 4-Et2NC6H4 (1a), 4-MeOC6H4 (1b), 4-MeC6H4 (1c), C6H5 (1d), 4-FC6H4 (1e), 4-ClC6H4 (1f), 4-O2NC6H4 (1g), 4-ClC6H4CH2 (1h), t-Bu (1i); dppe = Ph2PCH2CH2PPh2), or cis-[ReCl(CO)(dppe)2] (2), as well as trans-[FeBr(RCN)(depe)2]BF4 (3) (R = 4-MeOC6H4 (3a), 4-MeC6H4 (3b), C6H5 (3c), 4-FC6H4 (3d), 4-O2NC6H4 (3e), Me (3f), Et (3g), 4-MeOC6H4CH2 (3h); depe = Et2PCH2CH2PEt2), novel trans-[FeBr(CO)(depe)2]BF4 (4) and trans-[FeBr2(depe)2] (5) undergo, as revealed by cyclic voltammetry at a Pt-electrode and in aprotic non-aqueous medium, two consecutive reversible or partly reversible one-electron oxidations assigned as ReI → ReII → ReIII or FeII → FeIII → FeIV. The corresponding values of the oxidation potentials IE1/2ox and IIE1/2ox (waves I and II, respectively) correlate with the Pickett's and Lever's electrochemical ligand and metal site parameters. This allows to estimate these parameters for the various nitrile ligands, depe and binding sites (for the first time for a FeIII/IV couple). The electrochemical ligand parameter show dependence on the "electron-richness" of the metal centre. The values of IE1/2ox for the ReI complexes provide some supporting for a curved overall relationship with the sum of Lever's electrochemical ligand parameter. The Pickett parametrization for closed-shell complexes is extended now also to 17-electron complexes, i.e. with the 15-electron ReII and FeIII centres in cis-{[ReCl(dppe)2]}+ and trans-{FeBr(depe)2}2+, respectively.

Familial And Constitutional Moderate Bleeding Disorder Associated With Defective Platelet Cyclo-Oxygenase

1981 ◽  
Author(s):  
C Lecrubier ◽  
F Fouque ◽  
M Chignard ◽  
M H Horellou ◽  
J Conard ◽  
...  
Keyword(s):  
Autosomal Dominant ◽  
Atp Release ◽  
Rabbit Aorta ◽  
Total Radioactivity ◽  
Bleeding Disorder ◽  
Similar Extent ◽  
Synthetase Deficiency ◽  
Successive Generations ◽  
Second Wave ◽  
Rule Out

Three family members from two successive generations showed a moderate bleeding disorder. The bleeding times (Duke and Ivy-Borchgrevink) were both constantly prolonged. Platelet aggregation induced by ADP and adrenaline showed no second wave; collagen at low to moderate concentrations failed to aggregate and release ATP whereas higher amounts aggregated and released. Aggregation and release due to thrombin, ristocetin and synthetic epoxy derivatives (U 44069 and U 46619) were normal. Arachidonate (A.A.) was inactive and was not converted into thromboxane (TX) A2 activity evaluated on the rabbit aorta strip. The patient’s platelets did not respond to A.A. when PRP from an aspirin treated control was added. Platelet phospholipids (PL) were labelled by 14C - A.A. before stimulation by thrombin (T). Radioactivity of the PL of the propositus' platelets was affected with T to a similar extent as 5 laboratory controls, indicating that the phospholipase activity was not impaired. In contrast, no TXB2 was found: 0.9 p. cent as compared to 6 p. cent of total radioactivity in controls.Our data suggest a deficit in cyclo-oxygenase particularly since the levels of PGE2, PGF2a and PGD2 were within the limits of detection. These results seem to rule out the possibility of a TX-synthetase deficiency with excessive production of anti-aggregating PGs. This study suggests that transmission is autosomal dominant and confirms that cyclo-oxygenase is not needed for aggregation and ATP-release by high amounts of collagen.

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