GTPases in mammalian cells control critical processes including growth regulation (Ras family), cytoskeletal organization and cell-cycle progression (Rho family), and vesicle trafficking (Rab proteins). Because most GTPases are prenylated, and because most prenylated proteins in eukaryotic cells are GTPases (4), the study of protein prenylation and GTPases go hand in hand. Only a few CAAX-containing trypanosomatid GTPases have been cloned. Engman'slab (33) has cloned CAAX-containing DnaJ chaperone proteins from T. cruzi, and Hide's lab (34) cloned a T. brucei Ras/Rap-like protein. Eleven members of the Rab GTPase family (with CAC and CC termini) have been cloned from T. brucei and judging from their intracellular localizations are involved in endocytosis and exocytosis (35). The cloning ofseveral additional trypanosomatid Rab GTPases with C-terminal motifs CAC and CC (36,37) is helping to define secretory pathways in Leish-mania, T. cruzi, Giardia lamblia, Entamoeba histolytica, and Toxoplasma gondii. A more detailed description of trypanosomatid GTPases can be found in a recent review article by Field and coworkers (35).
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