CPAF: A Chlamydial Protease in Search of an Authentic Substrate

Allan L Chen,Christine Sütterlin,Jennifer K Lee,Ming Tan,Kirsten A Johnson,Craig R Roy

doi:10.1371/journal.ppat.1002842

Allan L Chen, Christine Sütterlin + Show 4 more

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https://doi.org/10.1371/journal.ppat.1002842

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Journal: PLoS Pathogens	Publication Date: Aug 2, 2012
Citations: 152	License type: CC BY 4.0

Affiliation: University of California, Irvine

Abstract

Bacteria in the genus Chlamydia are major human pathogens that cause an intracellular infection. A chlamydial protease, CPAF, has been proposed as an important virulence factor that cleaves or degrades at least 16 host proteins, thereby altering multiple cellular processes. We examined 11 published CPAF substrates and found that there was no detectable proteolysis when CPAF activity was inhibited during cell processing. We show that the reported proteolysis of these putative CPAF substrates was due to enzymatic activity in cell lysates rather than in intact cells. Nevertheless, Chlamydia-infected cells displayed Chlamydia-host interactions, such as Golgi reorganization, apoptosis resistance, and host cytoskeletal remodeling, that have been attributed to CPAF-dependent proteolysis of host proteins. Our findings suggest that other mechanisms may be responsible for these Chlamydia-host interactions, and raise concerns about all published CPAF substrates and the proposed roles of CPAF in chlamydial pathogenesis.

Highlights

Chlamydia are obligate intracellular bacteria that are responsible for more infections reported to the CDC than all other infectious agents combined [1]
Chlamydiae are proposed to cause many of these host-pathogen interactions through the cleavage or degradation of host proteins by the chlamydial protease CPAF, which is secreted into the host cytoplasm
We found that there was no detectable cleavage or degradation of 11 previously reported CPAF substrates in Chlamydia-infected cells and that CPAFmediated proteolysis of these host proteins occurs during cell harvest and lysis

Summary

Introduction

Chlamydia are obligate intracellular bacteria that are responsible for more infections reported to the CDC than all other infectious agents combined [1]. Chlamydia trachomatis causes the most prevalent bacterial sexually transmitted disease in the United States [2] and the most common form of preventable blindness worldwide [3] Another species, Chlamydia pneumoniae, is a causative agent of community-acquired pneumonia [4]. Chlamydiae replicate within a membrane-bound compartment called the chlamydial inclusion in which the bacterium converts between two specialized forms During this developmental cycle, chlamydiae usurp or subvert a number of processes within the host cell to support the infection. Chlamydia alters the host secretory pathway to acquire lipids from post-Golgi vesicles to support growth of the inclusion and bacterial replication [5,6,7] It blocks host cell apoptosis, which could otherwise be used as a host defense mechanism against this intracellular pathogen that requires 2–3 days to complete its developmental cycle [8,9,10]

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