Actin induction during PMA and cAMP-dependent signal pathway activation in Entamoeba histolytica trophozoites

Area of Science:

• Molecular Biology
• Parasitology
• Cell Signaling

Background:

• Protein kinase C (PKC) and cyclic AMP (cAMP)-dependent signaling pathways regulate actin rearrangements in Entamoeba histolytica.
• Actin dynamics are essential for parasite adhesion and locomotion, critical processes during host tissue invasion.

Purpose of the Study:

• To investigate the role of specific regulatory sequences (SRE and CRE) in the 5' regulatory region (5'RR) of an Entamoeba histolytica actin gene.
• To determine if these sequences mediate transcriptional upregulation of actin in response to PKC and cAMP signaling.

Main Methods:

• Stable transfection of Entamoeba histolytica with a plasmid containing the actin gene's 5'RR fused to a reporter gene (neomycin resistance, neo).
• Stimulation of transfected parasites with phorbol 12-myristate 13-acetate (PMA) and dibutyryl cyclic AMP (dcAMP).
• Measurement of neo and endogenous actin gene expression using constructs with intact or mutated/deleted 5'RR sequences.

Main Results:

• PMA and dcAMP induced significant upregulation of both neo and endogenous actin expression.
• A cooperative effect was observed between PMA and dcAMP in inducing neo expression.
• Induction of gene expression was abolished when the SRE and CRE motifs within the 5'RR were absent or mutated.
• Progressive deletions and site-directed mutations confirmed the critical role of SRE and CRE-like motifs in transcriptional regulation.

Conclusions:

• Specific PMA and cAMP-response elements (SRE and CRE-like motifs) within the actin gene's 5'RR are essential for mediating transcriptional activation.
• Coordinated action of PKC- and PKA-activated transcription factors regulates actin mRNA levels.
• These regulatory elements likely play a significant role in controlling actin expression and organization during Entamoeba histolytica's tissue invasion processes.