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Wang Q.-C.,University of Chinese Academy of Sciences | Zheng Q.,University of Chinese Academy of Sciences | Tan H.,Cleveland State University | Zhang B.,CAS Shanghai Institute of Materia Medica | And 18 more authors.
Cell | Year: 2016

Maintaining homeostasis of Ca2+ stores in the endoplasmic reticulum (ER) is crucial for proper Ca2+ signaling and key cellular functions. The Ca2+-release-activated Ca2+ (CRAC) channel is responsible for Ca2+ influx and refilling after store depletion, but how cells cope with excess Ca2+ when ER stores are overloaded is unclear. We show that TMCO1 is an ER transmembrane protein that actively prevents Ca2+ stores from overfilling, acting as what we term a "Ca2+ load-activated Ca2+ channel" or "CLAC" channel. TMCO1 undergoes reversible homotetramerization in response to ER Ca2+ overloading and disassembly upon Ca2+ depletion and forms a Ca2+-selective ion channel on giant liposomes. TMCO1 knockout mice reproduce the main clinical features of human cerebrofaciothoracic (CFT) dysplasia spectrum, a developmental disorder linked to TMCO1 dysfunction, and exhibit severe mishandling of ER Ca2+ in cells. Our findings indicate that TMCO1 provides a protective mechanism to prevent overfilling of ER stores with Ca2+ ions. © 2016 Elsevier Inc. All rights reserved.

Puffenberger E.G.,Clinic for Special Children | Puffenberger E.G.,Franklin And Marshall College | Jinks R.N.,Franklin And Marshall College | Wang H.,Center for Special Needs Children | And 13 more authors.
Human Mutation | Year: 2012

We studied a unique phenotype of cognitive delay, autistic behavior, and gait instability segregating in three separate sibships. We initiated genome-wide mapping in two sibships using Affymetrix 10K SNP Mapping Arrays and identified a homozygous 8.2 Mb region on chromosome 15 common to five affected children. We used exome sequencing of two affected children to assess coding sequence variants within the mapped interval. Four novel homozygous exome variants were shared between the two patients; however, only two variants localized to the mapped interval on chromosome 15. A third sibship in an Ohio Amish deme narrowed the mapped interval to 2.6 Mb and excluded one of the two novel homozygous exome variants. The remaining variant, a missense change in HERC2 (c.1781C>T, p.Pro594Leu), occurs in a highly conserved proline residue within an RCC1-like functional domain. Functional studies of truncated HERC2 in adherent retinal pigment epithelium cells suggest that the p.Pro594Leu variant induces protein aggregation and leads to decreased HERC2 abundance. The phenotypic correlation with the mouse Herc1 and Herc2 mutants as well as the phenotypic overlap with Angelman syndrome provide further evidence that pathogenic changes in HERC2 are associated with nonsyndromic intellectual disability, autism, and gait disturbance. © 2012 Wiley Periodicals, Inc.

Huang Q.,Cleveland State University | Zhou X.,Cleveland State University | Liu D.,Cleveland State University | Xin B.,Center for Special Needs Children | And 3 more authors.
Analytical Biochemistry | Year: 2014

Gangliosides are a family of glycosphingolipids characterized by mono- or polysialic acid-containing oligosaccharides linked through 1,3- and 1,4-β glycosidic bonds with subtle differences in structure that are abundantly present in the central nervous systems of many living organisms. Their cellular surface expression and physiological malfunction are believed to be pathologically implicated in considerable neurological disorders, including Alzheimer and Parkinson diseases. Recently, studies have tentatively elucidated that mental retardation or physical stagnation deteriorates as the physiological profile of gangliosides becomes progressively and distinctively abnormal during the development of these typical neurodegenerative syndromes. In this work, a reverse-phase liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay using standard addition calibration for determination of GM2, GM3, GD2, and GD3 in human plasma has been developed and validated. The analytes and internal standard were extracted from human plasma using a simple protein precipitation procedure. Then the samples were analyzed by reverse-phase ultra-performance liquid chromatography (UPLC)/MS/MS interfaced to mass spectrometry with electrospray ionization using a multiple reaction monitoring mode to obtain superior sensitivity and specificity. This assay was validated for extraction recovery, calibration linearity, precision, and accuracy. Our quick and sensitive method can be applied to monitor ganglioside levels in plasma from normal people and neurodegenerative patients. © 2014 Elsevier Inc. All rights reserved.

Huang Q.,Cleveland State University | Liu D.,Cleveland State University | Xin B.,Center for Special Needs Children | Cechner K.,Center for Special Needs Children | And 3 more authors.
Analytica Chimica Acta | Year: 2016

Gangliosides are found in abundance in the central nervous system of vertebrates. Their metabolic disruption and dysfunction are associated with various neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. In order to improve our understanding of the etiology of these diseases, analytical ganglioside assays with sufficient specificity and sensitivity in relevant biological matrices are required. In the present work we have developed and validated a reverse-phase ultra-performance liquid chromatography (UPLC)/tandem mass spectrometry (MS) method for determining monosialogangliosides GM1, GM2, and GM3 present in human plasma. Compared with our previous method, this method enhanced, by 15 fold, MS responses of the analytes by employing 2-(2-Pyridilamino)-ethylamine (PAEA) & 4-(4, 6-Dimethoxy-1, 3, 5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM)-based derivatization. The analytes and internal standards were derivatized with PAEA&DMTMM after extraction from plasma using a protein precipitation procedure. They were then purified using liquid-liquid partitioning. When the samples were then analyzed by UPLC-MS/MS with a multiple reaction monitoring (MRM) mode, we achieved superior sensitivity and specificity. This method was evaluated for extraction recovery, calibration linearity, precision, accuracy, and lower limit of quantification (LLOQ). The validated method was successfully applied to monitor monosialoganglioside levels in the plasma from patients with GM3 synthase deficiency. With significantly increased sensitivity, we have, for the first time, detected a significant amount of GM3 in the affected patients. © 2016.

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