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Cathepsin E: a novel target for regulation by class II transactivator
Christina S K Yee1, Yongxue Yao, Ping Li
1Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
Journal of Immunology (Baltimore, Md. : 1950)
|April 22, 2004
Summary
The MHC class II transactivator (CIITA) negatively regulates aspartic proteinase cathepsin E (CatE) expression and antigen processing. This regulation is isoform-dependent, impacting immune responses.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Cathepsin E (CatE) plays a role in antigen (Ag) processing.
- The MHC class II transactivator (CIITA) is crucial for MHC class II expression and antigen presentation.
Purpose of the Study:
- To investigate the regulatory relationship between CIITA and CatE expression.
- To determine the mechanism and specificity of CIITA-mediated regulation of CatE.
Main Methods:
- Analysis of CatE expression in CIITA-deficient and overexpressing cells (murine and human B cells, AGS cell line).
- Assessment of antigen processing (OVA) in cells with varying CIITA levels.
- Mapping of CIITA domains responsible for CatE regulation.
- Investigation of transcription factor involvement (PU.1, p300).
Main Results:
- CIITA deficiency led to increased CatE expression in B cells.
- CIITA overexpression reduced CatE mRNA and protein in AGS cells.
- CIITA suppressed OVA antigen processing, correlating with decreased CatE.
- Inhibition of CatE by CIITA was specific to the type III isoform and mapped to PST domains.
- CIITA reversed PU.1 and p300-induced CatE expression.
Conclusions:
- CIITA negatively regulates CatE expression and antigen processing in an isoform-dependent manner.
- This novel regulatory pathway highlights CIITA's broader role beyond MHC class II.
- Findings provide insights into immune response modulation via CatE control.