4-Hydroxy-2-nonenal Alkylated and Peroxynitrite Nitrated Proteins Localize to the Fused Mitochondria in Malpighian Epithelial Cells of Type IV CollagenDrosophilaMutants

Abstract

Background. Human type IV collagenopathy is associated with mutations within theCOL4A1and to a less extent theCOL4A2genes. The proteins encoded by these genes form heterotrimers and are the highest molar ratio components of the ubiquitous basement membrane. The clinical manifestations of theCOL4A1/A2mutations are systemic affecting many tissues and organs among these kidneys. In order to uncover the cellular and biochemical alterations associated with aberrant type IV collagen, we have explored the phenotype of the Malpighian tubules, the secretory organ and insect kidney model, incol4a1collagen gene mutants of the fruit flyDrosophila melanogaster. In Malpighian epithelial cells ofcol4a1mutants, robust mitochondrial fusion indicated mutation-induced stress. Immunohistochemistry detected proteins nitrated by peroxynitrite that localized to the enlarged mitochondria and increased level of membrane peroxidation, assessed by the amount of proteins alkylated by 4-hydroxy-2-nonenal that similarly localized to the fused mitochondria. Nuclei within the Malpighian epithelium showed TUNEL-positivity suggesting cell degradation. The results demonstrated thatcol4a1mutations affect the epithelia and, consequently, secretory function of the Malpighian tubules and provide mechanistic insight intocol4a1mutation-associated functional impairments not yet reported in human patients and in mouse models with mutantCOL4A1.