N-terminal cleavage of proTGFalpha occurs at the cell surface by a TACE-independent activity.

Abstract

ProTGFalpha (transforming growth factor alpha precursor) maturation and conversion into soluble TGFalpha is a complex process that involves three proteolytic steps. One, that occurs co-translationally, eliminates the signal sequence. Another, occurring at the juxta-membrane domain, solubilizes TGFalpha. A third cleavage removes the N-terminal extension of proTGFalpha. This latter step has been poorly studied, mainly because of the rapid kinetics of this cleavage. In the present study, we have designed a strategy to analyse several aspects regarding this N-terminal cleavage. In vivo treatment with the hydroxamate-based metalloprotease inhibitors BB3103 or TAPI-2 (tumour necrosis factor-alpha protease inhibitor 2) reversibly induced accumulation of forms of proTGFalpha that included the N-terminal extension. N-terminal shedding was rapid, and occurred at the cell surface. However, the machinery responsible for the N-terminal cleavage was inactive in other cellular sites, such as the endoplasmic reticulum. Experiments of proTGFalpha expression and maturation in cells deficient in TACE (tumour-necrosis-factor-alpha-converting enzyme) activity indicated that this protease was dispensable for N-terminal processing of proTGFalpha in vivo, but was required for regulated cleavage at the C-terminus. These findings indicate that TACE is not involved in N-terminal processing of proTGFalpha, and suggest differences in the machineries that control the cleavage at both ends of TGFalpha within its precursor.

• Authors: Pedro P Juanes, Laura Ferreira, Juan Carlos Montero, Joaquín Arribas, Atanasio Pandiella
• Journal: The Biochemical journal (Biochem J) Vol. 389 Issue Pt 1 Pg. 161-72 (Jul 01 2005) ISSN: 1470-8728 [Electronic] England
• PMID: 15777285 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Hydroxamic Acids
• Protease Inhibitors
• Protein Precursors
• Transforming Growth Factor alpha
• protransforming growth factor alpha
• Amyloid Precursor Protein Secretases
• Endopeptidases
• Aspartic Acid Endopeptidases
• BACE1 protein, human
• ADAM Proteins
• ADAM17 Protein
• ADAM17 protein, human

Topics

• ADAM Proteins (antagonists & inhibitors, metabolism)
• ADAM17 Protein
• Amyloid Precursor Protein Secretases
• Animals
• Aspartic Acid Endopeptidases
• CHO Cells
• Cell Membrane (metabolism)
• Cricetinae
• Dose-Response Relationship, Drug
• Endopeptidases (metabolism)
• Endoplasmic Reticulum (metabolism)
• HeLa Cells
• Humans
• Hydroxamic Acids (pharmacology)
• Protease Inhibitors (pharmacology)
• Protein Precursors (chemistry, metabolism)
• Protein Processing, Post-Translational (drug effects)
• Transforming Growth Factor alpha (chemistry, metabolism)