Human ERK1 induces filamentous growth and cell wall remodeling pathways in Saccharomyces cerevisiae.
Expression of an activated extracellular signal-regulated kinase 1 (ERK1) construct in yeast cells was used to examine the conservation of function among mitogen-activated protein (MAP) kinases. Sequence alignment of the human MAP kinase ERK1 with all Saccharomyces cerevisiae kinases reveals a particularly strong kinship with Kss1p (invasive growth promoting MAP kinase), Fus3p (pheromone response MAP/ERK kinase), and Mpk1p (cell wall remodeling MAP kinase). A fusion protein of constitutively active human MAP/ERK kinase 1 (MEK) and human ERK1 was introduced under regulated expression into yeast cells. The fusion protein (MEK/ERK) induced a filamentation response element promoter and led to a growth retardation effect concomitant with a morphological change resulting in elongated cells, bipolar budding, and multicell chains. Induction of filamentous growth was also observed for diploid cells following MEK/ERK expression in liquid culture. Neither haploids nor diploids, however, showed marked penetration of agar medium. These effects could be triggered by either moderate MEK/ERK expression at 37 degrees C or by high level MEK/ERK expression at 30 degrees C. The combination of high level MEK/ERK expression and 37 degrees C resulted in cell death. The deleterious effects of MEK/ERK expression and high temperature were significantly mitigated by 1 m sorbitol, which also enhanced the filamentous phenotype. MEK/ERK was able to constitutively activate a cell wall maintenance reporter gene, suggesting misregulation of this pathway. In contrast, MEK/ERK effectively blocked expression from a pheromone-responsive element promoter and inhibited mating. These results are consistent with MEK/ERK promoting filamentous growth and altering the cell wall through its ability to partially mimic Kss1p and stimulate a pathway normally controlled by Mpk1p, while appearing to inhibit the normal functioning of the structurally related yeast MAP kinase Fus3p.
Atienza
J M
JM
Department of Biological Chemistry and the Molecular Biology Institute, UCLA School of Medicine, Los Angeles, CA 90095, USA.
Suh
M
M
Xenarios
I
I
Landgraf
R
R
Colicelli
J
J
D002455:Cell Division / Q000235:genetics*; D002473:Cell Wall / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D017930:Genes, Reporter; D006801:Humans; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010641:Phenotype; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D013012:Sorbitol / Q000494:pharmacology
D005656:Fungal Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D013012:Sorbitol; C075580:FUS3 protein, S cerevisiae; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases