Systemic lupus erythematosus: molecular cloning of fourteen recombinant DNase monoclonal kappa light chains with different catalytic properties

Abstract

Background: DNase antibodies can play an important role in the pathogenesis of different autoimmune pathologies.

Methods: An immunoglobulin light chain phagemid library derived from peripheral blood lymphocytes of patients with systemic lupus erythematosus (SLE) was used. The small pools of phage particles displaying DNA binding light chains with different for DNA were isolated by affinity chromatography on DNA-cellulose and the fraction eluted with 0.5M NaCl was used for preparation of individual monoclonal light chains (MLChs, 28kDa). Forty-five of 451 individual colonies were randomly chosen for a study of MLChs with DNase activity. The clones were expressed in Escherichia coli in a soluble form, and MLChs were purified by metal chelating chromatography followed by gel filtration, and studied in detail.

Results: Fifteen of 45 MLChs efficiently hydrolyzed DNA, and fourteen of them demonstrated various optimal concentrations of KCl or NaCl in a 1-100mM range and showed one or two pH optima in a 4.8-9.1 range. All MLChs were dependent on divalent metal cations: the ratio of relative DNase activity in the presence of Mn(2+), Ca(2+), Mg(2+), Ni(2+), Zn(2+), Cu(2+), and Co(2+) was individual for each MLCh preparation. Fourteen MLChs demonstrated a comparable affinity for DNA (260-320nM), but different kcat values (0.02-0.7min(-1)).

Conclusions: These observations suggest an extreme diversity of DNase abzymes from SLE patients.

General significance: SLE light chain repertoire can serve as a source of new types of DNases.

Keywords: DNase activity; Extreme diversity; Recombinant monoclonal light chain; Systemic lupus erythematosus.