Membrane protein band 3 alteration associated with neurologic disease and tissue-reactive antibodies

Abstract

Immunological analogues of band 3, the anion transporter, have been identified in all cells that have been studied, including both isolated neurons and neurons of the central nervous system. We studied band 3 structural/functional relationships in a family in which the proposita has a serious, progressive, genetic neurologic disorder with acanthocytosis (choreoacanthocytosis). Biochemical studies of erythrocytes from the proposita, her mother and brother revealed that maximal sulfate transport velocity (Vmax) and sodium transport were increased, glucose efflux was decreased. Ankyrin binding was normal. Immunologic studies revealed increased IgG binding to middle-aged cells of the proposita and her brother, binding of antibodies to aged band 3 to a distinct region of band 3 in erythrocyte membranes in immunoblots, and binding of choreoacanthocytosis sera IgG to erythroid and brain band 3 and synthetic peptides of band 3 in immunoblots. Antibodies to neural and, to a lesser extent, renal tissue were observed in choreoacanthocytosis sera. These antibodies appear to have a band 3 specificity. Monoclonal antibodies to 150 residues of the carboxyl terminus of band 3 stained two band 3 fragments in immunoblots of chymotrypsin-digested membranes that are not present in control cells. This suggests that band 3 is altered in this autosomal recessive neurologic disorder. In addition, these monoclonal antibodies stained five band 3 breakdown products in membranes of untreated red cells in both control and choreoacanthocytosis cells. The possibility that a disturbance of some function of band 3 may contribute to the neurologic abnormalities in affected individuals is intriguing. This is the first evidence for abnormalities of membrane transport in the neurologic disorder known as choreoacanthocytosis.