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APRIL/TRDL-1, a tumor necrosis factor-like ligand, stimulates cell death
1The Huntsman Cancer Institute, Division of Molecular Pharmacology, Salt Lake City, Utah 84112, USA.
Abstract:
We have examined the activity of a new member of the tumor necrosis factor (TNF) family identified through Expressed Sequence Tag database searching using TNFalpha protein as the search query. We have termed this protein TNF-related death ligand-la (TRDL-1alpha). Traditional cDNA library screening identified two additional splice variants designated TRDL-1beta and TRDL-1gamma that differed from TRDL-1alpha by the deletion of two small regions within the protein coding region. TRDL-1alpha is identical in sequence to the recently described molecule, APRIL, that may induce cell proliferation. We found, however, that purified, FLAG-tagged TRDL-1alpha caused Jurkat cell death with kinetics that paralleled FasL. In vitro binding experiments demonstrated that TRDL-1alpha coprecipitated Fas and HVEM and suggested TRDL-1alpha as an alternate ligand for these receptors. TRDL-1 localized to chromosome 17p13.3 and its expression was widespread in normal tissues. Examination of 48 tumor samples revealed high levels of TRDL-1 expression in several tumors, including those from the gastrointestinal tract. Expression of TRDL-1 in COS-1 cells confirmed membrane association of TRDL-1, typical of TNF family members.
Insights
A novel tumor necrosis factor (TNF) family member, TRDL-1alpha (also known as APRIL), induces cell death and interacts with Fas and HVEM receptors. This protein is expressed in normal tissues and elevated in several gastrointestinal tract tumors.
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- The tumor necrosis factor (TNF) superfamily plays critical roles in immunity, inflammation, and cell death.
- Identification of novel TNF family members is crucial for understanding complex biological processes and disease pathogenesis.
Purpose of the Study:
- To identify and characterize a novel TNF family member, termed TNF-related death ligand-1alpha (TRDL-1alpha).
- To investigate the biological activity, receptor interactions, and expression patterns of TRDL-1alpha and its splice variants.
Main Methods:
- Expressed Sequence Tag (EST) database searching using TNFalpha as a query.
- cDNA library screening to identify splice variants (TRDL-1beta, TRDL-1gamma).
- In vitro cell death assays using Jurkat cells and purified FLAG-tagged TRDL-1alpha.
- In vitro binding experiments (coprecipitation) with Fas and HVEM.
- Chromosomal localization and tissue expression analysis (normal tissues and tumor samples).
- Expression analysis in COS-1 cells to confirm membrane association.
Main Results:
- TRDL-1alpha was identified and found to be identical to APRIL.
- TRDL-1alpha induced Jurkat cell death, similar to FasL.
- TRDL-1alpha coprecipitated with Fas and HVEM, suggesting it as an alternate ligand.
- TRDL-1 localized to chromosome 17p13.3 with widespread expression in normal tissues.
- Elevated TRDL-1 expression was observed in several tumors, including gastrointestinal cancers.
- TRDL-1 exhibited membrane association, characteristic of TNF family members.
Conclusions:
- TRDL-1alpha is a functional TNF family member with potent cell death-inducing activity.
- TRDL-1alpha represents an alternative ligand for Fas and HVEM receptors.
- The widespread expression in normal tissues and elevated levels in tumors suggest a role for TRDL-1 in both normal physiology and cancer development.