title: Asn-Linked Glycosylation Contributes to Surface Expression and Voltage-Dependent Gating of Cav1.2 Ca²⁺ Channel.
abstract: The Cav1.2 Ca2+ channel is essential for cardiac and smooth muscle contractility and many physiological functions. We mutated single, double, and quadruple sites of the four potential Asn (N)-glycosylation sites in the rabbit Cav1.2 into Gln (Q) to explore the effects of Nglycosylation. When a single mutant (N124Q, N299Q, N1359Q, or N1410Q) or Cav1.2/WT was expressed in Xenopus oocytes, the biophysical properties of single mutants were not significantly different from Cav1.2/WT. In comparison, the double mutant N124,299Q showed a positive shift in voltage-dependent gating. Furthermore, the quadruple mutant (QM; N124,299,1359,1410Q) showed a positive shift in voltage-dependent gating as well as a reduction of current. We tagged EGFP to the QM, double mutants, and Cav1.2/WT to chase the mechanisms underlying the reduced currents of QM. The surface fluorescence intensity of QM was weaker than that of Cav1.2/WT, suggesting that the reduced current of QM arises from its lower surface expression than Cav1.2/WT. Tunicamycin treatment of oocytes expressing Cav1.2/WT mimicked the effects of the quadruple mutations. These findings suggest that Nglycosylation contributes to the surface expression and voltage-dependent gating of Cav1.2.
authors.affiliation: Department of Life Science, Sogang University, Seoul 121-742, Republic of Korea.
authors.forename: Hyun-Jee
authors.initials: HJ
authors.lastname: Park
authors.affiliation: Department of Life Science, Sogang University, Seoul 121-742, Republic of Korea.
authors.forename: Se-Hong
authors.initials: SH
authors.lastname: Min
authors.affiliation: Department of Life Science, Sogang University, Seoul 121-742, Republic of Korea.
authors.forename: Yu-Jin
authors.initials: YJ
authors.lastname: Won
authors.affiliation: Department of Life Science, Sogang University, Seoul 121-742, Republic of Korea.
authors.forename: Jung-Ha
authors.initials: JH
authors.lastname: Lee
mesh_terms: D000818:Animals; D055592:Biophysical Phenomena; D020746:Calcium Channels, L-Type / Q000235:genetics / Q000378:metabolism*; D004252:DNA Mutational Analysis; D006031:Glycosylation; D020125:Mutation, Missense; D017354:Point Mutation; D011499:Protein Processing, Post-Translational; D011817:Rabbits; D014981:Xenopus
chemical_list: D020746:Calcium Channels, L-Type; C419385:L-type calcium channel alpha(1C)
keywords: Cav1.2 Ca2+ channel; N-glycosylation; Xenopus oocyte; point mutation; voltage clamping