© 1999 by The Society for Integrative and Comparative Biology
Heat Shock as a Regular Feature of the Life Cycle of Leishmania Parasites1
Bernhard Nocht Institute for Tropical Medicine D-20359 Hamburg, Germany
Correspondence: 2 Corresponding author: E-mail: clos{at}bni.unihamburg.de
The heat shock response in kinetoplastid protozoa is distinguished from the stress response of the metazoa and yeasts by a lack of regulated transcription and by the failure to respond to stresses other than heat. The heat stress encountered by the parasites during transmission into mammalian hosts is a key trigger for their stage differentiation and may be a factor in the tropism of Leishmania species. While the major heat shock proteins are highly abundant both in the arthropod stage and the mammalian stage of the parasites, the 100 kD heat shock protein of L. major and L. donovani, Hsp100, appears to be expressed and required primarily in the mammalian stages of these parasites. Gene replacement mutants deficient in Hsp100 expression fail to express certain proteins specific for the amastigote and display markedly reduced virulence and aberrant morphology in infection experiments. However, the effects of leishmanial Hsp100 on general thermotolerance, induced or uninduced, are marginal at best. We conclude that the role of Hsp100 has been adapted to the specific needs of a parasite which has to enter stage conversion under heat stress and which has no need for tolerance against extreme stress.