Perturbations of the actin cytoskeleton activate a Dictyostelium STAT signalling pathway

Area of Science:

• Cellular Biology
• Molecular Biology
• Biochemistry

Background:

• Dictyostelium transcription factor STATc is activated by tyrosine phosphorylation under hyper-osmotic stress or DIF-1.
• STATc deactivation is mediated by the tyrosine phosphatase PTP3, whose activity is regulated by serine phosphorylation.
• Stress-induced PTP3 serine phosphorylation inhibits its phosphatase activity, leading to STATc activation.

Purpose of the Study:

• To investigate the role of PTP3 serine phosphorylation in STATc activation by DIF-1.
• To explore the relationship between cytoskeletal remodeling and STATc activation.
• To determine if F-actin polymerization status influences PTP3 activity and STATc signaling.

Main Methods:

• Western blotting to detect PTP3 serine phosphorylation (specifically S747).
• Analysis of F-actin distribution using microscopy.
• Treatment with DIF-1, hyper-osmotic stress, and actin polymerization inhibitors (latrunculin A, cytochalasin A).

Main Results:

• PTP3 serine residue S747 is phosphorylated in response to DIF-1, similar to stress conditions.
• DIF-1 induces transient F-actin redistribution and cell rounding, mimicking stress responses.
• Inhibitors of actin polymerization (latrunculin A, cytochalasin A) induce S747 phosphorylation and STATc activation.

Conclusions:

• PTP3 phosphorylation at S747 is a common mechanism for STATc activation by both stress and DIF-1.
• Cytoskeletal remodeling, particularly changes in F-actin polymerization, plays a regulatory role in PTP3 activity.
• STATc activation is linked to cellular responses involving cytoskeletal dynamics during stress and developmental signaling.