Evidence that the ubiquitin proteolytic pathway is involved in the degradation of precipitated globin chains in thalassaemia

Ultrastructural immunocytochemical studies were performed on sections of bone marrow from three patients with beta-thalassaemia major and two patients with haemoglobin H (HbH) disease. Some sections were reacted with either a polyclonal or a monoclonal anti-human-ubiquitin antibody and the reaction visualized using a gold-labelled secondary antibody. The inclusions of precipitated globin chains found within the erythropoietic cells of all five patients reacted much more strongly than the surrounding inclusion-free cytoplasm with both of the anti-ubiquitin antibodies, indicating that the precipitated globin chains were ubiquitinated. A non-specific reaction between the anti-ubiquitin antibodies and the inclusions was excluded by demonstrating that various other antibodies, including a polyclonal anti-human cathepsin D antibody, did not react with the inclusions. The data suggest that the ubiquitin proteolytic pathway is involved in the degradation of precipitated globin chains in alpha- and beta-thalassaemia.