PMID:12397063

Citation	Ellis, JG 4th, Davila, M and Chakrabarti, R (2003) Potential involvement of extracellular signal-regulated kinase 1 and 2 in encystation of a primitive eukaryote, Giardia lamblia. Stage-specific activation and intracellular localization. J. Biol. Chem. 278:1936-45
Abstract	Mitogen-activated protein kinase (MAPK) pathways are major signaling systems by which eukaryotic cells convert environmental cues to intracellular events such as proliferation and differentiation. We have identified Giardia lamblia homologues of two members of the MAPK family ERK1 and ERK2. Functional characterization of giardial ERK1 and ERK2 revealed that both kinases were expressed in trophozoites and encysting cells as 44- and 41-kDa polypeptides, respectively, and were catalytically active. Analysis of the kinetic parameters of the recombinant proteins showed that ERK2 is approximately 5 times more efficient than ERK1 in phosphorylating myelin basic protein as a substrate, although the phosphorylating efficiency of the native ERK1 and ERK2 appeared to be the same. Immunofluorescence analysis of the subcellular localization of ERK1 and ERK2 in trophozoites showed ERK1 staining mostly in the median body and in the outer edges of the adhesive disc and ERK2 staining in the nuclei and in the caudal flagella. Our study also showed a noticeable change in the subcellular distribution of ERK2 during encystation, which became more punctate and mostly cytoplasmic, but no significant change in the ERK1 localization at any time during encystation. Interestingly, both ERK1 and ERK2 enzymes exhibited a significantly reduced kinase activity during encystation reaching a minimum at 24 h, except for an initial approximately 2.5-fold increase in the ERK1 activity at 2 h, which resumed back to the normal levels at 48 h despite no apparent change in the expression level of either one of these kinases in encysting cells. A reduced concentration of the phosphorylated ERK1 and ERK2 was also evident in these cells at 24 h. Our study suggests a functional distinction between ERK1 and ERK2 and that these kinases may play a critical role in trophozoite differentiation into cysts.
Links	PubMed Online version:10.1074/jbc.M209274200
Keywords	Amino Acid Sequence; Animals; Base Sequence; Catalysis; DNA Primers; Fluorescent Antibody Technique; Giardia lamblia/enzymology; Giardia lamblia/physiology; Mitogen-Activated Protein Kinase 1/chemistry; Mitogen-Activated Protein Kinase 1/metabolism; Mitogen-Activated Protein Kinase 3; Mitogen-Activated Protein Kinases/chemistry; Mitogen-Activated Protein Kinases/metabolism; Molecular Sequence Data; Phosphorylation; Recombinant Proteins/chemistry; Recombinant Proteins/metabolism; Sequence Homology, Amino Acid; Subcellular Fractions/enzymology
edit table

Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
GIAIN:Q8IS82		GO:0097568: median body	ECO:0000314:		C		Immunofluorescence microscopy shows the location of the protein. Figure 6	complete CACAO 10744
GIAIN:Q8IS82		GO:0097597: ventral disc	ECO:0000314:		C		Immunofluorescence analysis was used to locate the protein. Figure 6	complete CACAO 10745
GIAIN:Q8IS82	part_of	GO:0097568: median body	ECO:0000314: direct assay evidence used in manual assertion		C		Seeded From UniProt	complete
GIAIN:Q8IS82	part_of	GO:0097597: ventral disc	ECO:0000314: direct assay evidence used in manual assertion		C		Seeded From UniProt	complete
GIAIN:Q8IS81		GO:0005929: cilium	ECO:0000314:		C		Immunofluorescence analysis was used to identify the location of the protein. Figure 7	complete CACAO 10747
GIAIN:Q8IS81		GO:0005634: nucleus	ECO:0000314:		C		Immunofluorescence analysis of was used to identify the location of the protein. Figure 7	complete CACAO 10748
GIAIN:Q8IS81	part_of	GO:0005929: cilium	ECO:0000314: direct assay evidence used in manual assertion		C		Seeded From UniProt	complete
GIAIN:Q8IS81	part_of	GO:0005634: nucleus	ECO:0000314: direct assay evidence used in manual assertion		C		Seeded From UniProt	complete

References

See Help:References for how to manage references in GONUTS.