Actin Recovery and Bud Emergence in Osmotically Stressed Cells Requires the Conserved Actin Interacting Mitogen-activated Protein Kinase Kinase Kinase Ssk2p/MTK1 and the Scaffold Protein Spa2p

AUTOR(ES)

Yuzyuk, Tatiana

FONTE

The American Society for Cell Biology

RESUMO

Osmotic stress causes actin cytoskeleton disassembly, a cell cycle arrest, and activation of the high osmolarity growth mitogen-activated protein kinase pathway. A previous study showed that Ssk2p, a mitogen-activated protein kinase kinase kinase of the high osmolarity growth pathway, promotes actin cytoskeleton recovery to the neck of late cell cycle, osmotically stressed yeast cells. Data presented herein examined the role of Ssk2p in actin recovery early in the cell cycle. We found that actin recovery at all stages of the cell cycle is not controlled by Ssk1p, the known activator of Ssk2p, but required a polarized distribution of Ssk2p as well as its actin-interacting and kinase activity. Stress-induced localization of Ssk2p to the neck required the septin Shs1p, whereas localization to the bud cortex depended on the polarity scaffold protein Spa2p. spa2Δ cells, like ssk2Δ cells, were defective for actin recovery from osmotic stress. These spa2Δ defects could be suppressed by overexpression of catalytically active Ssk2p. Furthermore, Spa2p could be precipitated by GST-Ssk2p from extracts of osmotically stressed cells. The Ssk2p mediated actin recovery pathway seems to be conserved; MTK1, a human mitogen-activated protein kinase kinase kinase of the p38 stress response pathway and Ssk2p homolog, was also able to localize at polarized growth sites, form a complex with actin and Spa2p, and complement actin recovery defects in osmotically stressed ssk2Δ and spa2Δ yeast cells. We hypothesize that osmotic stress-induced actin disassembly leads to the formation of an Ssk2p–actin complex and the polarized localization of Ssk2p. Polarized Ssk2p associates with the scaffold protein Spa2p in the bud and Shs1p in the neck, allowing Ssk2p to regulate substrates involved in polarized actin assembly.

Documentos Relacionados

• The JIP Group of Mitogen-Activated Protein Kinase Scaffold Proteins
• Negative Regulation of Protein Translation by Mitogen-Activated Protein Kinase-Interacting Kinases 1 and 2
• A Conserved p38 Mitogen-Activated Protein Kinase Pathway Regulates Drosophila Immunity Gene Expression
• MAPKAP kinase-2; a novel protein kinase activated by mitogen-activated protein kinase.
• The structure of mitogen-activated protein kinase p38 at 2.1-Å resolution