4-Hydroxy-2-Nonenal-Modified Glyceraldehyde-3-Phosphate Dehydrogenase Is Degraded by Cathepsin G in Rat Neutrophils

Yukihiro Tsuchiya,Shigeki Kobayashi,Go Okada,Toshiyuki Chikuma,Hiroshi Hojo

doi:10.1155/2011/213686

Abstract

Degradation of oxidized or oxidatively modified proteins is an essential part of the antioxidant defenses of cells. 4-Hydroxy-2-nonenal, a major reactive aldehyde formed by lipid peroxidation, causes many types of cellular damage. It has been reported that 4-hydroxy-2-nonenal-modified proteins are degraded by the ubiquitin-proteasome pathway or, in some cases, by the lysosomal pathway. However, our previous studies using U937 cells showed that 4-hydroxy-2-nonenal-modified glyceraldehyde-3-phosphate dehydrogenase is degraded by cathepsin G. In the present study, we isolated the 4-hydroxy-2-nonenal-modified glyceraldehyde-3-phosphate dehydrogenase-degrading enzyme from rat neutrophils to an active protein fraction of 28 kDa. Using the specific antibody, the 28 kDa protein was identified as cathepsin G. Moreover, the degradation activity was inhibited by cathepsin G inhibitors. These results suggest that cathepsin G plays a crucial role in the degradation of 4-hydroxy-2-nonenal-modified glyceraldehyde-3-phosphate dehydrogenase.

Highlights

Low-to-moderate concentrations of reactive oxygen species affect a great number of physiological functions
Various reactive aldehydes, such as 2-alkenals, 4-hydroxy-2alkenals, and ketoaldehydes, are generated [5]. 4-Hydroxy2-nonenal (HNE) is a major reactive aldehyde formed by the peroxidation of ω-6 polyunsaturated fatty acids, such as linoleic acid and arachidonic acid [6], and is involved in various physiological and pathological reactions [5, 6]
We indicated that GAPDH modified by HNE or by acetylleucine chloromethyl ketone, a synthetic inhibitor of acylpeptide hydrolase, is degraded enzymatically and is accompanied by the release of a 23 kDa fragment in the U937 leukemia cell line [24, 25]

Summary

Introduction

Low-to-moderate concentrations of reactive oxygen species affect a great number of physiological functions. The binding of HNE to proteins can cause conformational changes and amino acid modifications, as well as the accumulation and aggregation of proteins which causes cellular dysfunctions [16] The breakdown of such modified proteins is an essential defense mechanism against oxidative stress in cells. After phagocytosis of microorganisms or other particulate substances, neutrophils secrete a variety of mediators that possess potent proinflammatory and antimicrobial activities These mediators include a group of antibiotic peptides and proteases that are stored in neutrophil granules and released during the process of degranulation. Neutrophil proteases are associated with systemic vasculitis, such as Wegener’s granulomatosis This type of vasculitis can affect multiple organs including the lungs and kidneys and is characterized by granulomatous inflammation. We examined whether cathepsin G in the conditioned medium from these activated cells is effective in HNE-modified GAPDH degradation

Results

Discussion

Materials and Methods