title: Immunoglobulin light chains activate tubular epithelial cells through redox signaling.
abstract: The renal proximal tubule metabolizes circulating low-molecular-weight proteins such as Ig free light chains. In the setting of plasma cell dyscrasias, the burden of filtered protein can be very high. Endocytosis of certain nephrotoxic light chains induces H(2)O(2) production and monocyte chemoattractant protein-1 (MCP-1) release, leading to recruitment of inflammatory cells and interstitial fibrosis, but how these processes are linked mechanistically is not well understood. This study investigated the relationship between H(2)O(2) generated after light chain endocytosis by human proximal tubular (HK-2) cells and activation of c-Src, a redox-sensitive tyrosine kinase. HK-2 cells exposed to two different light chains upregulated c-Src activity, which increased the production of MCP-1. In parallel, we observed a time-dependent oxidation of c-Src. Inhibition of c-Src activity and silencing c-Src expression abrogated the light chain-induced MCP-1 response, but had no effect on H(2)O(2), indicating that production of H(2)O(2) is upstream of c-Src in the signaling cascade. Silencing megalin and cubilin expression inhibited the MCP-1 response, whereas extracellular catalase did not, indicating that endocytosis is required and that intracellular generation of reactive oxygen species activates c-Src. These data show that intracellular H(2)O(2) induced by endocytosis of monoclonal free light chains oxidizes and activates c-Src, which promotes release of MCP-1.
authors.affiliation: University of Birmingham, Edgbaston, Birmingham, United Kingdom.
authors.forename: Kolitha
authors.initials: K
authors.lastname: Basnayake
authors.forename: Wei-Zhong
authors.initials: WZ
authors.lastname: Ying
authors.forename: Pei-Xuan
authors.initials: PX
authors.lastname: Wang
authors.forename: Paul W
authors.initials: PW
authors.lastname: Sanders
mesh_terms: D000418:Albumins / Q000378:metabolism; D000081247:CSK Tyrosine-Protein Kinase; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D004847:Epithelial Cells / Q000166:cytology / Q000502:physiology*; D055785:Gene Knockdown Techniques; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D007147:Immunoglobulin Light Chains / Q000502:physiology*; D015850:Interleukin-6 / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000502:physiology*; D026561:Low Density Lipoprotein Receptor-Related Protein-2 / Q000235:genetics / Q000378:metabolism; D010084:Oxidation-Reduction; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D019061:src-Family Kinases
chemical_list: D000418:Albumins; C111835:CCL2 protein, human; D018932:Chemokine CCL2; D007147:Immunoglobulin Light Chains; D015850:Interleukin-6; D026561:Low Density Lipoprotein Receptor-Related Protein-2; D017382:Reactive Oxygen Species; D011956:Receptors, Cell Surface; C029486:intrinsic factor-cobalamin receptor; D006861:Hydrogen Peroxide; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human