title: Neuronal Calcium Sensor 1 Has Two Variants with Distinct Calcium Binding Characteristics.
abstract: Neuronal calcium sensor-1 (NCS-1 Var1) is a calcium-binding protein expressed in most tissues. We examined a poorly characterized variant of NCS-1 (Var2), identified only in humans where the N-terminal 22 amino acid residues of native NCS-1(MGKSNSKLKPEVVEELTRKTY) were replaced with 4 different residues (MATI). Because alterations in the level of expression of NCS-1 Var1 and the expression of NCS-1 variants have been correlated with several neurological diseases, the relative expression and functional role of NCS-1 Var2 was examined. We found that NCS-1 Var2 mRNA levels are not found in mouse tissues and are expressed at levels ~1000-fold lower than NCS-1 Var1 in three different human cell lines (SHSY5Y, HEK293, MB231). Protein expression of both variants was only identified in cell lines overexpressing exogenous NCS-1 Var2. The calcium binding affinity is ~100 times weaker in purified NCS-1 Var2 than NCS-1 Var1. Because truncation of NCS-1 Var1 has been linked to functional changes in neurons, we determined whether the differing properties of the NCS-1 variants could potentially contribute to the altered cell function. In contrast to previous reports showing that overexpression of NCS-1 Var1 increases calcium-dependent processes, functional differences in cells overexpressing NCS-1 Var2 were undetectable in assays for cell growth, cell death and drug (paclitaxel) potency. Our results suggest that NCS-1 Var1 is the primary functional version of NCS-1.
authors: Department of Stomatology, Xiang Ya Hospital, Central South University, Changsha, Hunan, China.|Department of Pharmacology, Yale University, New Haven, Connecticut, United States of America.
authors: Baisheng
authors: B
authors: Wang
authors: Department of Pharmacology, Yale University, New Haven, Connecticut, United States of America.
authors: Göran R
authors: GR
authors: Boeckel
authors: Department of Pharmacology, Yale University, New Haven, Connecticut, United States of America.
authors: Larry
authors: L
authors: Huynh
authors: Department of Pharmacology, Yale University, New Haven, Connecticut, United States of America.
authors: Lien
authors: L
authors: Nguyen
authors: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, United States of America.
authors: Wenxiang
authors: W
authors: Cao
authors: Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, United States of America.
authors: Enrique M
authors: EM
authors: De La Cruz
authors: Yale Comprehensive Cancer Center, New Haven, Connecticut, United States of America.
authors: Edward J
authors: EJ
authors: Kaftan
authors: Department of Pharmacology, Yale University, New Haven, Connecticut, United States of America.|Yale Comprehensive Cancer Center, New Haven, Connecticut, United States of America.|Department of Cellular and Molecular Physiology, Yale University, New Haven, Connecticut, United States of America.
authors: Barbara E
authors: http://orcid.org/0000-0001-9657-9704
authors: BE
authors: Ehrlich
mesh_terms: D017398:Alternative Splicing; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D057809:HEK293 Cells; D006801:Humans; D051580:Neuronal Calcium-Sensor Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D009479:Neuropeptides / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011485:Protein Binding; D017510:Protein Folding; D013045:Species Specificity; D014018:Tissue Distribution
chemical_list: D051580:Neuronal Calcium-Sensor Proteins; D009479:Neuropeptides; C101464:frequenin calcium sensor proteins; D002118:Calcium