Abstract
The sexual Fus3 MAP kinase module of yeast is highly conserved in eukaryotes and transmits external signals from the plasma membrane to the nucleus. We show here that the module of the filamentous fungus Aspergillus nidulans (An) consists of the AnFus3 MAP kinase, the upstream kinases AnSte7 and AnSte11, and the AnSte50 adaptor. The fungal MAPK module controls the coordination of fungal development and secondary metabolite production. It lacks the membrane docking yeast Ste5 scaffold homolog; but, similar to yeast, the entire MAPK module's proteins interact with each other at the plasma membrane. AnFus3 is the only subunit with the potential to enter the nucleus from the nuclear envelope. AnFus3 interacts with the conserved nuclear transcription factor AnSte12 to initiate sexual development and phosphorylates VeA, which is a major regulatory protein required for sexual development and coordinated secondary metabolite production. Our data suggest that not only Fus3, but even the entire MAPK module complex of four physically interacting proteins, can migrate from plasma membrane to nuclear envelope.
Highlights
Eukaryotic organisms communicate between cell surface and nucleus to respond to environmental signals
Tagged AnFus3 recruited the transcription factor AnSte12 [SteA] by tandem affinity purification (TAP) only when the fungus was induced for sexual development but not during vegetative filamentous growth or asexual development (Figure 1B, Table S1)
We describe here the A. nidulans Fus3 mitogenactivated protein kinase (MAPK) module which is involved in sexual development and the control of secondary metabolism and releases AnFus3 into the nucleus
Summary
Eukaryotic organisms communicate between cell surface and nucleus to respond to environmental signals. The sexual pathway of the budding yeast Saccharomyces cerevisiae represents a paradigm for signal transduction in eukaryotes [3,4,5] This MAP kinase pathway responds to pheromones and induces differentiation processes which trigger sexual mating of yeast [4,6]. Binding of pheromone to the transmembrane receptors Ste or Ste, which are coupled to guanine nucleotide binding proteins (G protein, G protein coupled receptor: GPCR), initiates signal transduction. This induces the release of the Gbc subunit from the trimeric Gabc protein. Preactivated Ste is localized in the membrane and initiates the kinase cascade system by phosphorylating the MAP3K Ste11 [4]
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