June 2021
Volume 62, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2021
Changes in expression of regulators of protein phosphatase 2A are observed in lacrimal gland from a murine model of Sjögren’s syndrome
Author Affiliations & Notes
  • Minchang Choi
    Department of Pharmacology and Pharmaceutical Sciences, University of Southern California School of Pharmacy, Los Angeles, California, United States
  • Hao Guo
    Department of Pharmacology and Pharmaceutical Sciences, University of Southern California School of Pharmacy, Los Angeles, California, United States
  • Maria Edman
    Department of Ophthalmology, University of Southern California Keck School of Medicine, Los Angeles, California, United States
  • Sarah F Hamm-Alvarez
    Department of Ophthalmology, University of Southern California Keck School of Medicine, Los Angeles, California, United States
    Department of Pharmacology and Pharmaceutical Sciences, University of Southern California School of Pharmacy, Los Angeles, California, United States
  • Footnotes
    Commercial Relationships   Minchang Choi, None; Hao Guo, None; Maria Edman, None; Sarah Hamm-Alvarez, None
  • Footnotes
    Support  RO1 EY0011386, P30 EY02922, unrestricted departmental grant from Research to Prevent Blindness
Investigative Ophthalmology & Visual Science June 2021, Vol.62, 3467. doi:
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      Minchang Choi, Hao Guo, Maria Edman, Sarah F Hamm-Alvarez; Changes in expression of regulators of protein phosphatase 2A are observed in lacrimal gland from a murine model of Sjögren’s syndrome. Invest. Ophthalmol. Vis. Sci. 2021;62(8):3467.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Sjögren’s Syndrome (SS) is a systemic autoimmune disease associated with lymphocytic infiltration and loss of function of the lacrimal gland (LG). The cysteine protease, cathepsin S (CTSS), is increased in LG and tears in a murine model of SS; moreover, the protease’s activity is elevated in SS patients’ tears. Inhibition of CTSS activity in a murine model also suppressed ocular symptoms of SS. Protein phosphatase 2A (PP2A), through dephosphorylation of tristetraprolin (TTP), destabilizes CTSS mRNA; conversely, inhibition of PP2A leads to increased stability and expression of CTSS mRNA. To understand more about the mechanisms responsible for LG CTSS upregulation in SS, we have explored the expression of effectors of the PP2A-TTP pathway in LG from SS model and healthy control mice.

Methods : Age-matched (12-18 weeks) male NOD mice and male BALB/c mice LG were used to compare gene and protein expression of the PP2A-TTP axis components. Primers for PP2A catalytic subunit, TTP, SET (an endogenous PP2A inhibitor), and CIP2A (an endogenous PP2A inhibitor) were used for analysis by RT-qPCR of lysed LG cDNA. CIP2A protein expression in LG lysates from male NOD and BALB/c mouse LG were compared by Western Blotting. PP2A and CTSS activities were measured from male mouse BALB/c LG incubated ex vivo with either okadaic acid (OKA, 1uM), a commercially available PP2A inhibitor, or DMSO (vehicle) for 2 hr using commercially available kits PP2A (Milipore Cat # 17-313) and CTSS (Biovision Cat # K144).

Results : NOD mouse LG showed significantly less expression of PP2Ac mRNA compared to BALB/c mouse LG (n=4, p=0.0054). A comparable trend to increased expression of CIP2A, an endogenous PP2A inhibitor, was seen in NOD mouse LG (n=6, p=0.0663). This trend to increased expression was verified by Western blotting for CIP2A, showing an increase of 1.6 fold CIP2A (n=6, p=0.011) in NOD mouse LG lysates relative to BALB/c mouse. No significant changes in gene expression of SET or TTP were seen between strains. Lysates from BALB/c mouse LG ex vivo incubated with OKA showed a 2.2 fold increase in CTSS activity (n=5, p=0.0013) and a 0.6 fold decrease in PP2A activity (n=3, p=0.0395) compared to control.

Conclusions : Changes in expression of effectors of the PP2A-TTP pathway regulating CTSS mRNA stability suggest this as a possible mechanism governing increased expression of CTSS in SS.

This is a 2021 ARVO Annual Meeting abstract.

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