Date on Master's Thesis/Doctoral Dissertation

12-2010

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Biochemistry and Molecular Biology

Committee Chair

Klinge, Carolyn Muriel

Author's Keywords

MUC1; Dry eye disease; Inflammation; Cytokines; TNFa; Splice variants

Subject

Dry eye syndromes; Cornea--Diseases

Abstract

Mucin 1 (MUC1) is a plasma membrane-bound glycoprotein that plays a protective role in corneal epithelial cells. Two full-length splice variants of MUCl: MUCl/B and MUCl/A, that differ by the inclusion of 27 bp from intron 1 and a SNP in MUCl/A, but have identical C-terminal cytoplasmic domain (CD) sequences, were identified in human conjunctival tissue. I tested the hypothesis that MUC1 splice variants are key immunoregulators that act on the ocular surface to protect the ocular surface from inflammation and that their expression correlates with dry eye status. The expression of MUC1/A and MUCl/B splice variant was examined in non-Sjogren's aqueous deficient and evaporative dry eye patients and compared to normal controls. The frequency of MUC1/A gene expression was lower in patients with non-Sjogren's aqueous deficient dry eye compared to controls, indicating a link between MUC1/A and the symptoms associated with dry eye disease. Overexpression of MUC1/A and MUC1/B in COS-7 cells resulted in equal protein expression and plasma membrane localization. MUCl/B and MUCl/A splice variants differed in their ability to modulate the TNFa-induced inflammatory responses. The MUCl/B splice variant, and not MUCl/A, inhibited the induction of IL-1ß and IL-8 expression by TNFa at 4 h. In contrast, MUC1/A stimulated TNFa-driven IL-8 mRNA and protein expression after 24 h of treatment. MUC1/B, but not MUC1/A, inhibited TNFa-induced luciferase activity from an NF-KB reporter. Both MUC1/B and MUCl/A blocked the induction of miR-21 by TNFa. In addition, MUC1/A, but not MUCl/B, increased basal expression of TGFß. These data demonstrate for the first time that MUCl/A and MUC1/B are genetic susceptibility factors with different anti-inflammatory activities.

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