NATURAL-RESISTANCE TO INFECTION WITH INTRACELLULAR PATHOGENS - CROSS-TALK BETWEEN NRAMP1 AND LPS GENES

This study was designed to analyze the association of Nramp1 and/or Lp s genes with differential protein expression in macrophages in order t o select candidate proteins that might be related to resistance/suscep tibility to various microbial infections under the control of the Nram p1 and/or Lps genes. The macrophage cell lines derived from bone marro w of Nrampl or Lps congenic mice were utilized and high-resolution two -dimensional electrophoreis (2-DE), separating proteins according to t heir charge and size, was used as a window into alterations in gene ex pression and a means to compare the macrophages carrying a resistant a llele of Nramp1 gene and/or normal allele of Lps gene, with: their cou nterparts carrying either a susceptible allele of Nramp1 or defective allele of the Lps gene. We demonstrate that the changes of constitutiv e levels of two proteins named according to their isoelectric point/mo lecular weight (pI/M-r), p6.6/25 and p7.0/22, discriminate satisfactor ily not only the macrophages congenic at the Nramp1 gene but also the macrophages congenic at the Lps gene, thus reflecting their common gen otype (Nramp1(r), Lps(n)). Furthermore, the decreased constitutive lev els of these proteins in macrophages carrying a defective allele of Lp s but preserving a resistant allele of Nramp1 can be, at least in part , restored by stimulation with interferon gamma or lipopolysaccharide. 2-DE immunoblot analysis identified the p7.0/22 protein as manganese superoxide dismutase. Bcl-2 appears to be the best candidate for p6.6/ 25 as suggested by 2-DE quantitative alterations and Western blot anal ysis. These proteins are important in the regulation of intracellular redox balance and the regulation of apoptosis in macrophages and their alterations might reflect closely the transport functions of ions or other charged substrates suggested for Nramp1 protein.