Trypsin digestion increases Na(+)-H+ exchange rates in native rabbit brush border membrane.
Experiments were designed to examine the effects of trypsin-mediated proteolysis on the activity of the rabbit renal brush border membrane Na(+)-H+ exchanger. Incubation of brush border membrane vesicles with trypsin resulted in a concentration and time-dependent change in proton gradient-stimulated sodium uptake. Extensive trypsin digestion resulted in a marked decrease in the activity of the transporter. By contrast, limited trypsin digestion resulted in a significant increase in proton gradient-stimulated, amiloride-inhibitable sodium uptake. Sodium-dependent proton efflux was also significantly increased by limited trypsin digestion. The passive permeability of the vesicles to sodium and protons, and the sodium-dependent and sodium-independent uptake of glucose were not affected by limited trypsin digestion. These data indicate that limited trypsin digestion increases the activity of the renal brush border membrane Na(+)-H+ exchanger. It is suggested that the renal Na(+)-H+ exchanger contains one or more inhibitory components or sites which are sensitive to inactivation by limited trypsin-mediated proteolysis.
Department of Medicine, University of California, Los Angeles.
E J
EJ
Weinman
D A
DA
Steplock
S
S
Shenolikar
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002463:Cell Membrane Permeability; D005947:Glucose / Q000378:metabolism; D066298:In Vitro Techniques; D007668:Kidney / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D007700:Kinetics; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism*; D011522:Protons; D011817:Rabbits; D012964:Sodium / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers; D014357:Trypsin / Q000378:metabolism* / Q000494:pharmacology
D002352:Carrier Proteins; D011522:Protons; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; D012964:Sodium; D014357:Trypsin; D005947:Glucose