期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 107, 期 13, 页码 5961-5966出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0911991107
关键词
autosomal dominant retinitis pigmentosa; endoplasmic reticulum stress; adeno-associated virus; unfolded protein response
资金
- Foundation Fighting Blindness [TA-GT-4090-0479-UFL, TA-GT-0507-0384]
- National Institutes of Health [EY13729, EY11123, EY08571, EY01919, EY06842, EY02162, EY018313, EY013280]
- That Man May See, Inc.
- Research to Prevent Blindness
- Macular Vision Research Foundation
- Juvenile Diabetes Research Foundation
- Hope for Vision
The P23H mutation within the rhodopsin gene (RHO) causes rhodopsin misfolding, endoplasmic reticulum (ER) stress, and activates the unfolded protein response (UPR), leading to rod photoreceptor degeneration and autosomal dominant retinitis pigmentosa (ADRP). Grp78/BiP is an ER-localized chaperone that is induced by UPR signaling in response to ER stress. We have previously demonstrated that BiP mRNA levels are selectively reduced in animal models of ADRP arising from P23H rhodopsin expression at ages that precede photoreceptor degeneration. We have now overexpressed BiP to test the hypothesis that this chaperone promotes the trafficking of P23H rhodopsin to the cell membrane, reprograms the UPR favoring the survival of photoreceptors, blocks apoptosis, and, ultimately, preserves vision in ADRP rats. In cell culture, increasing levels of BiP had no impact on the localization of P23H rhodopsin. However, BiP overexpression alleviated ER stress by reducing levels of cleaved pATF6 protein, phosphorylated eIF2 alpha and the proapoptotic protein CHOP. In P23H rats, photoreceptor levels of cleaved ATF6, pEIF2 alpha, CHOP, and caspase-7 were much higher than those of wild-type rats. Subretinal delivery of AAV5 expressing BiP to transgenic rats led to reduction in CHOP and photoreceptor apoptosis and to a sustained increase in electroretinogram amplitudes. We detected complexes between BiP, caspase-12, and the BH3-only protein BiK that may contribute to the antiapoptotic activity of BiP. Thus, the preservation of photoreceptor function resulting from elevated levels of BiP is due to suppression of apoptosis rather than to a promotion of rhodopsin folding.
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