PKCα Is Recruited toStaphylococcus aureus-Containing Phagosomes and Impairs Bacterial Replication by Inhibition of Autophagy.

Maria Celeste Gauron,María Isabel Colombo,Alexandra C Newton

doi:10.3389/fimmu.2021.662987

Abstract

Hijacking the autophagic machinery is a key mechanism through which invasive pathogens such as Staphylococcus aureus replicate in their host cells. We have previously demonstrated that the bacteria replicate in phagosomes labeled with the autophagic protein LC3, before escaping to the cytoplasm. Here, we show that the Ca2+-dependent PKCα binds to S. aureus-containing phagosomes and that α-hemolysin, secreted by S. aureus, promotes this recruitment of PKCα to phagosomal membranes. Interestingly, the presence of PKCα prevents the association of the autophagic protein LC3. Live cell imaging experiments using the PKC activity reporter CKAR reveal that treatment of cells with S. aureus culture supernatants containing staphylococcal secreted factors transiently activates PKC. Functional studies reveal that overexpression of PKCα causes a marked inhibition of bacterial replication. Taken together, our data identify enhancing PKCα activity as a potential approach to inhibit S. aureus replication in mammalian cells.

Highlights

Autophagy is a cellular degradative process that plays an essential role in cellular homeostasis, and in clearing infection by certain pathogens, a process known as xenophagy
Since DAG is required for activation of most members of the Protein Kinase C (PKC) family, we first asked whether the surface of the phagosomal membrane was conducive to PKC activation by assessing whether DAG was located in the S. aureus phagosomal membrane
After demonstrating that the conventional isozyme PKCa is recruited to the phagosomes where S. aureus resides during its invasion, and that the secreted factors produced by the bacterium activate the kinase, we examined whether this enzyme regulates the autophagic response that is induced during infection

Summary

Introduction

Autophagy is a cellular degradative process that plays an essential role in cellular homeostasis, and in clearing infection by certain pathogens, a process known as xenophagy. Xenophagy is a selective defense mechanism by which, once microorganisms are recognized by the cell, proteins known as autophagic adaptors/receptors recruit LC3 and components of the autophagic machinery toward them [1,2,3,4]. Many invasive bacterial pathogens, including species of Salmonella, Shigella and Mycobacterium, induce an autophagic response in host cells, which leads to the degradation of these pathogens or partial restriction of their intracellular growth [5,6,7]. The generated autophagic response is occasionally unsuccessful, as some microorganisms are able to manipulate this pathway for their own benefit in order to survive and replicate in the host cells [8].

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Results

Conclusion