First published online February 20, 2008
Journal of Cell Science 121, 503e (2008)
© The Company of Biologists Limited
AP3 aids acido-calcisomes
The trypanosomatid parasite Leishmania and other unicellular organisms contain acidocalcisomes–acidic organelles that are rich in calcium and polyphosphate, and have been proposed to play a role in osmoregulation and pH maintenance. Acidocalcisomes share key features with certain lysosome-related organelles, but their relationship with the endosomal-lysosomal system remains unclear. On page 561, Jeremy Mottram and colleagues investigate the effect of the adaptor protein complex AP3, which plays a role in lysosomal sorting, on acidocalcisome function. Using mutants of L. major that lack a necessary AP3 subunit, the authors show that the absence of AP3 has no apparent effect on lysosomal function. By contrast, acidocalcisomes within the mutant cells store less polyphosphate and contain lower levels of vacuolar proton pyrophosphatase; consequently, the mutant cells are deficient in proton transport and the pH within acidocalcisomes is higher. Notably, the mutant cells are unable to produce lesions in the footpads of mice. The function of acidocalcisomes is therefore dependent on AP3, implying that acidocalcisomes are closely related to the endosomal-lysosomal system.
Related articles in JCS:
- The AP3 adaptor is involved in the transport of membrane proteins to acidocalcisomes of Leishmania
- Sébastien Besteiro, Daniela Tonn, Laurence Tetley, Graham H. Coombs, and Jeremy C. Mottram
JCS 2008 121: 561-570.
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