Modulation of V-ATPase by βA3/A1-crystallin in retinal pigment epithelial cells

Mallika Valapala, Yuri Sergeev, Eric Wawrousek, Stacey Hose, J. Samuel Zigler, Debasish Sinha

Research output: Chapter in Book/Report/Conference proceedingChapter

Abstract

We have previously demonstrated that βA3/A1-crystallin, a member of the β/γ-crystallin superfamily, is expressed in the astrocytes and retinal pigment epithelial (RPE) cells of the eye. In order to understand the physiological functions of βA3/A1-crystallin in RPE cells, we generated conditional knockout (cKO) mice where Cryba1, the gene encoding βA3/A1-crystallin, is deleted specifically from the RPE using the Cre-loxP system. By utilizing the cKO model, we have shown that this protein is required by RPE cells for proper lysosomal degradation of photoreceptor outer segments (OS) that have been internalized in phagosomes and also for the proper functioning of the autophagy process. We also reported that βA3/A1-crystallin is trafficked to lysosomes, where it regulates endolysosomal acidification by modulating the activity of the lysosomal V-ATPase complex. Our results show that the V-ATPase activity in cKO RPE is significantly lower than WT RPE. Since, V-ATPase is important for regulating lysosomal pH, we noticed that endolysosomal pH was higher in the cKO cells compared to the WT cells. Increased lysosomal pH in cKO RPE is also associated with reduced Cathepsin D activity. Cathepsin D is a major lysosomal aspartic protease involved in the degradation of the OS and hence we believe that reduced proteolytic activity contributes to impaired degradation of OS in the cKO RPE. Reduced lysosomal activity in the cKO RPE also contributes to the incomplete degradation of the autophagosomes. Our results also suggest that βA3/A1-crystallin regulates V-ATPase activity by binding to the V0 subunit of the V-ATPase complex. Taken together, these results suggest a novel mechanism by which βA3/A1-crystallin regulates lysosomal function by modulating the activity of V-ATPase.

Original languageEnglish (US)
Title of host publicationAdvances in Experimental Medicine and Biology
PublisherSpringer New York LLC
Pages779-784
Number of pages6
Volume854
DOIs
StatePublished - Oct 1 2016

Publication series

NameAdvances in Experimental Medicine and Biology
Volume854
ISSN (Print)00652598
ISSN (Electronic)22148019

Fingerprint

Crystallins
Retinal Pigments
Adenosine Triphosphatases
Epithelial Cells
Modulation
Degradation
Cathepsin D
Phagosomes
Gene encoding
Acidification
Autophagy
Lysosomes
Knockout Mice
Astrocytes
Peptide Hydrolases

Keywords

  • Autophagy
  • Lysosomes
  • Phagocytosis
  • Retinal pigment epithelial cells
  • βA3/A1-crystallin

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

Cite this

Valapala, M., Sergeev, Y., Wawrousek, E., Hose, S., Zigler, J. S., & Sinha, D. (2016). Modulation of V-ATPase by βA3/A1-crystallin in retinal pigment epithelial cells. In Advances in Experimental Medicine and Biology (Vol. 854, pp. 779-784). (Advances in Experimental Medicine and Biology; Vol. 854). Springer New York LLC. https://doi.org/10.1007/978-3-319-17121-0_104

Modulation of V-ATPase by βA3/A1-crystallin in retinal pigment epithelial cells. / Valapala, Mallika; Sergeev, Yuri; Wawrousek, Eric; Hose, Stacey; Zigler, J. Samuel; Sinha, Debasish.

Advances in Experimental Medicine and Biology. Vol. 854 Springer New York LLC, 2016. p. 779-784 (Advances in Experimental Medicine and Biology; Vol. 854).

Research output: Chapter in Book/Report/Conference proceedingChapter

Valapala, M, Sergeev, Y, Wawrousek, E, Hose, S, Zigler, JS & Sinha, D 2016, Modulation of V-ATPase by βA3/A1-crystallin in retinal pigment epithelial cells. in Advances in Experimental Medicine and Biology. vol. 854, Advances in Experimental Medicine and Biology, vol. 854, Springer New York LLC, pp. 779-784. https://doi.org/10.1007/978-3-319-17121-0_104
Valapala M, Sergeev Y, Wawrousek E, Hose S, Zigler JS, Sinha D. Modulation of V-ATPase by βA3/A1-crystallin in retinal pigment epithelial cells. In Advances in Experimental Medicine and Biology. Vol. 854. Springer New York LLC. 2016. p. 779-784. (Advances in Experimental Medicine and Biology). https://doi.org/10.1007/978-3-319-17121-0_104
Valapala, Mallika ; Sergeev, Yuri ; Wawrousek, Eric ; Hose, Stacey ; Zigler, J. Samuel ; Sinha, Debasish. / Modulation of V-ATPase by βA3/A1-crystallin in retinal pigment epithelial cells. Advances in Experimental Medicine and Biology. Vol. 854 Springer New York LLC, 2016. pp. 779-784 (Advances in Experimental Medicine and Biology).
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