Identification of the Protein Kinases Pyk3 and Phg2 as Regulators of the STATc-Mediated Response to Hyperosmolarity

Autor: Linh Hai Vu, Ludwig Eichinger, Tsuyoshi Araki, Jeffrey G. Williams, Christoph S. Clemen, Jianbo Na
Jazyk: angličtina
Rok vydání: 2014
Předmět:
Protozoan Proteins
lcsh:Medicine
Protein tyrosine phosphatase
Signal transduction
Biochemistry
chemistry.chemical_compound
0302 clinical medicine
Molecular cell biology
Transcriptional regulation
Dictyostelium
Phosphorylation
lcsh:Science
Regulation of gene expression
0303 health sciences
Multidisciplinary
Kinase
Dictyostelium Discoideum
Protein-Tyrosine Kinases
Signaling Cascades
Cell biology
Nucleic acids
STAT Transcription Factors
DNA modification
Research Article
DNA transcription
Signaling in cellular processes
Active Transport
Cell Nucleus
Biology
Signaling Pathways
Stress Signaling Cascade
03 medical and health sciences
Model Organisms
Osmotic Pressure
Genetics
Protein kinase A
030304 developmental biology
STAT signaling family
Cell Nucleus
Protozoan Models
lcsh:R
DNA
chemistry
Phosphoserine
Mutation
lcsh:Q
Gene expression
Protein Tyrosine Phosphatases
030217 neurology & neurosurgery
Zdroj: PLoS ONE
PLoS ONE, Vol 9, Iss 2, p e90025 (2014)
ISSN: 1932-6203
Popis: Cellular adaptation to changes in environmental osmolarity is crucial for cell survival. In Dictyostelium, STATc is a key regulator of the transcriptional response to hyperosmotic stress. Its phosphorylation and consequent activation is controlled by two signaling branches, one cGMP- and the other Ca(2+)-dependent, of which many signaling components have yet to be identified. The STATc stress signalling pathway feeds back on itself by upregulating the expression of STATc and STATc-regulated genes. Based on microarray studies we chose two tyrosine-kinase like proteins, Pyk3 and Phg2, as possible modulators of STATc phosphorylation and generated single and double knock-out mutants to them. Transcriptional regulation of STATc and STATc dependent genes was disturbed in pyk3(-), phg2(-), and pyk3(-)/phg2(-) cells. The absence of Pyk3 and/or Phg2 resulted in diminished or completely abolished increased transcription of STATc dependent genes in response to sorbitol, 8-Br-cGMP and the Ca(2+) liberator BHQ. Also, phospho-STATc levels were significantly reduced in pyk3(-) and phg2(-) cells and even further decreased in pyk3(-)/phg2(-) cells. The reduced phosphorylation was mirrored by a significant delay in nuclear translocation of GFP-STATc. The protein tyrosine phosphatase 3 (PTP3), which dephosphorylates and inhibits STATc, is inhibited by stress-induced phosphorylation on S448 and S747. Use of phosphoserine specific antibodies showed that Phg2 but not Pyk3 is involved in the phosphorylation of PTP3 on S747. In pull-down assays Phg2 and PTP3 interact directly, suggesting that Phg2 phosphorylates PTP3 on S747 in vivo. Phosphorylation of S448 was unchanged in phg2(-) cells. We show that Phg2 and an, as yet unknown, S448 protein kinase are responsible for PTP3 phosphorylation and hence its inhibition, and that Pyk3 is involved in the regulation of STATc by either directly or indirectly activating it. Our results add further complexities to the regulation of STATc, which presumably ensure its optimal activation in response to different environmental cues.
Databáze: OpenAIRE
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