Purification and Characterization of (H++K+)-ATPase from Hog Gastric Mucosa

Potential role of bacterial lipopolysaccharides in the development of autoimmune gastritis induced by neonatal thymectomy

The role of LPS in the development of autoimmune gastritis (AIG) in BALB/c mice thymectomized on day 3 after birth (d3-Tx) was investigated in LPS-non-responder BALB/lpsdmice. The symptoms were classified into three types: (i) hypertrophic stomach (HS) and lymphocyte infiltration (LI)-double negative; (ii) HS-negative and LI-positive; and (iii) HS- and LI-double positive. The double positive type-3 was termed AIG. Following d3-Tx, LPS-responder BALB/c ( Lpsn) mice showed the following incidence: type-1 (14%), type-2 (14%) and type-3 (72%). In contrast, the incidence in BALB/lpsdmice was 67%, 22% and 11%, respectively. Thus the frequency of AIG development in BALB/lpsdmice was much lower than in BALB/c mice. A single administration of LPS on day 2 post-d3-Tx induced severe AIG incidence in all d3-Tx BALB/c mice but not in d3-Tx BALB/lpsdmice, suggesting that LPS influences the progression of AIG development. Formation of auto-antibodies against the proton pump (H+/K+-ATPase) seemed to be related to AIG incidence in d3-Tx BALB/c mice. In d3-Tx BALB/lpsdmice, however, higher levels of auto-antibodies were detected in the type-2 mice, whereas AIG incidence was much lower than that in d3-Tx BALB/c mice. Thus, formation of auto-antibodies against the proton pump in d3-Tx BALB/lpsdmice does not appear to correlate with AIG pathogenesis.

Binding domain of oligomycin on Na(+),K(+)-ATPase

Oligomycin inhibits Na(+),K(+)-ATPase activity by stabilizing the Na(+) occlusion but not the K(+) occlusion. To locate the binding domain of oligomycin on Na(+),K(+)-ATPase, the tryptic-digestion profile of Na(+),K(+)-ATPase was compared with the profile of Na(+) occlusion within the digested Na(+),K(+)-ATPase in the presence of oligomycin. The Na(+) occlusion profile is responsible for the digestion profile of the alpha-subunit, which is the catalytic subunit of the ATPase. The effect of oligomycin on chimeric Ca(2+)-ATPase activity was examined. The chimera used, in which the 163 N-terminal amino acids of chicken sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase 1 were replaced with the 200 N-terminal amino acids of the chicken Na(+),K(+)-ATPase alpha1-subunit, partially retains the Na(+)-dependent characteristics of Na(+), K(+)-ATPase, because the chimeric Ca(2+)-ATPase activity is activated by Na(+) but inhibited by ouabain, a specific inhibitor of Na(+),K(+)-ATPase (Ishii, T., Lemas, M.V., Takeyasu, K., 1994, Proc. Natl. Acad. Sci. U. S. A., 91, 6103-6107). Oligomycin depressed the activation by Na(+) of the chimeric Ca(2+)-ATPase activity. These findings suggest that the 200 N-terminal amino acids of the Na(+), K(+)-ATPase alpha-subunit include a binding domain for oligomycin.