An endogenous chemorepellent directs cell movement by inhibiting pseudopods at one side of cells

Area of Science:

• Cell biology
• Biochemistry
• Molecular biology

Background:

• Eukaryotic cells navigate using chemoattraction pathways, often involving G protein-coupled receptors and signaling cascades like PI3K/Akt/PKB.
• Chemorepulsion mechanisms in eukaryotes remain less understood compared to chemoattraction.
• AprA is a previously identified chemorepellent protein secreted by Dictyostelium discoideum.

Purpose of the Study:

• To delineate the specific signal transduction pathway utilized by the AprA chemorepellent in Dictyostelium discoideum.
• To compare and contrast the molecular mechanisms of chemorepulsion with known chemoattraction pathways.

Main Methods:

• Utilized 29 distinct Dictyostelium cell lines with targeted disruptions in cAMP and/or AprA signaling pathway components.
• Analyzed the cellular responses to AprA exposure, focusing on pseudopod formation and cellular localization.

Main Results:

• The AprA chemorepulsion pathway engages components including Ras, protein kinase A (PKA), target of rapamycin (TOR), phospholipase A, and ERK1.
• AprA-mediated chemorepulsion does not require the PI3 kinase/Akt/PKB or guanylyl cyclase pathways.
• Unlike chemoattraction, AprA does not induce actin polymerization or increase pseudopod formation rate; instead, it inhibits pseudopod formation on the cell side nearest the repellent source.

Conclusions:

• AprA employs a distinct subset of signaling pathways for chemorepulsion, diverging significantly from established chemoattraction routes.
• The absence of PI3K/Akt/PKB and guanylyl cyclase involvement in AprA signaling explains the differential effects on cell morphology and movement.
• This study elucidates a novel chemorepulsion mechanism, providing insights into eukaryotic cell navigation and response to external chemical cues.