Spectrum of Cav1.4 dysfunction in congenital stationary night blindness type 2

Burtscher, Verena and Schicker, Klaus and Bhargava, Anamika and et al, . (2014) Spectrum of Cav1.4 dysfunction in congenital stationary night blindness type 2. Biochimica et Biophysica Acta (BBA) - Biomembranes, 1838 (8). pp. 2053-2065. ISSN 00052736

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Abstract

Defective retinal synaptic transmission in patients affected with congenital stationary night blindness type 2 (CSNB2) can result from different dysfunction phenotypes in Cav1.4 L-type calcium channels. Here we investigated two prototypical Cav1.4 variants from either end of the functional spectrum. Using whole-cell and single-channel patch-clamp techniques, we provide analysis of the biophysical characteristics of the point mutation L860P and the C-terminal truncating mutation R1827X. L860P showed a typical loss-of-function phenotype attributed to a reduced number of functional channels expressed at the plasma membrane as implied by gating current and non-stationary noise analyses. This phenotype can be rationalized, because the inserted proline is predicted to break an amphipatic helix close to the transmembrane segment IIIS1 and thus to reduce channel stability and promote misfolding. In fact, L860P was subject to an increased turnover. In contrast, R1827X displayed an apparent gain-of-function phenotype, i.e., due to a hyperpolarizing shift of the IV-curve and increased single-channel activity. However, truncation also resulted in the loss of functional C-terminal modulation and thus unmasked calcium-dependent inactivation. Thus R1827X failed to support continuous calcium influx. Current inactivation curtails the dynamic range of photoreceptors (e.g., when adapting to variation in illumination). Taken together, the analysis of two representative mutations that occur in CSNB2 patients revealed fundamental differences in the underlying defect. These may explain subtle variations in the clinical manifestation and must be taken into account, if channel function is to be restored by pharmacochaperones or related approaches.

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IITH Creators:
IITH CreatorsORCiD
Bhargava, Anamikahttp://orcid.org/0000-0002-1048-3427
Item Type: Article
Uncontrolled Keywords: L-type calcium channel Cav1.4 Calcium channelopathy Congenital stationary night blindness type 2
Subjects: Others > Biotechnology
Divisions: Department of Biotechnology
Depositing User: Library Staff
Date Deposited: 20 Aug 2019 05:59
Last Modified: 20 Aug 2019 05:59
URI: http://raiith.iith.ac.in/id/eprint/5960
Publisher URL: http://doi.org/10.1016/j.bbamem.2014.04.023
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