The yeast model for batten disease: mutations in BTN1, BTN2, and HSP30 alter pH homeostasis.
The BTN1 gene product of the yeast Saccharomyces cerevisiae is 39% identical and 59% similar to human CLN3, which is associated with the neurodegenerative disorder Batten disease. Furthermore, btn1- Delta strains have an elevated activity of the plasma membrane H(+)-ATPase due to an abnormally high vacuolar acidity during the early phase of growth. Previously, DNA microarray analysis revealed that btn1- Delta strains compensate for the altered plasma membrane H(+)-ATPase activity and vacuolar pH by elevating the expression of the two genes HSP30 and BTN2. We now show that deletion of either HSP30 or BTN2 in either BTN1(+) or btn1- Delta strains does not alter vacuolar pH but does lead to an increased activity of the vacuolar H(+)-ATPase. Deletion of BTN1, BTN2, or HSP30 does not alter cytosolic pH but diminishes pH buffering capacity and causes poor growth at low pH in a medium containing sorbic acid, a condition known to result in disturbed intracellular pH homeostasis. Btn2p was localized to the cytosol, suggesting a role in mediating pH homeostasis between the vacuole and plasma membrane H(+)-ATPase. Increased expression of HSP30 and BTN2 in btn1- Delta strains and diminished growth of btn1- Delta, hsp30- Delta, and btn2- Delta strains at low pH reinforce our view that altered pH homeostasis is the underlying cause of Batten disease.[1]References
- The yeast model for batten disease: mutations in BTN1, BTN2, and HSP30 alter pH homeostasis. Chattopadhyay, S., Muzaffar, N.E., Sherman, F., Pearce, D.A. J. Bacteriol. (2000) [Pubmed]
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