Trypanosoma brucei: Two mitogen activated protein kinase kinases are dispensable for growth and virulence of the bloodstream form

Abstract

Mitogen activated protein kinase cascades function in eukaryotic responses to the environment and stress. Trypanosomatid parasites possess protein kinases with sequences characteristic of kinases in such cascades. In this report we use gene knockouts to demonstrate that two mitogen activated kinase kinase genes, MKK1 (Tb927.3.4860) and MKK5 (Tb927.10.5270), are not essential in the pathogenic bloodstream stage of Trypanosoma brucei, either in vitro or in vivo. Bloodstream forms lacking MKK1 showed decreased growth at 39°C as compared to the parental line. However, unlike its Leishmania orthologue, T. brucei MKK1 does not appear to play a significant role in flagellar biogenesis.

MAP kinase kinase 1 (MKK1) is essential for transmission of Trypanosoma brucei by Glossina morsitans

“…1A). As previously reported for null mutants of MKK1 in monomorphic bloodstream forms [14], there was no growth defect ( Fig. 1B), nor were there discernable alterations to the flagellum (data not shown).…”

“…Recently, null mutants of two T. brucei MKKs, MKK1 and MKK5, were described [14]. Neither gene was essential for slender bloodstream forms, but the MKK1 null mutant was slightly more sensitive than its wild-type parent to being cultured at 39 • C. In contrast to its Leishmania orthologue, T. brucei MKK1 did not play a significant role in flagellar biogenesis.…”

“…Indeed the only prey identified in this screen was the mitochondrial RNA editing ligase REL1 [20]. Since MKK1 is cytoplasmic in trypanosomes [14], an interaction between the two proteins is hard to reconcile with their different locations and putative functions.…”

“…It has been shown recently that MKK1 is not essential for bloodstream forms [14]. To investigate the requirement for MKK1 in other life-cycle stages we generated null mutants in procyclic forms of a fly-transmissible strain.…”

Mitogen-Activated Protein Kinase Kinase 5 Regulates Proliferation and Biosynthetic Processes in Procyclic Forms of Trypanosoma brucei

“…The knockout of these genes in bloodstream forms did not cause changes in cell growth in standard culture conditions; however, defects in proliferation were observed upon exposure to temperature stress 13 . Interestingly, in the same work, western blot analysis suggested that MKK5 expression is higher in the procyclic than in the bloodstream forms of T. brucei 13 , which may indicate that the role of this protein is developmental stage-specific. To date, the function of MKK5 in procyclic forms of T. brucei has not yet been addressed.…”