Chlamydia trachomatis is a medically significant human pathogen and is an epithelial-tropic obligate intracellular parasite. Invasion of nonprofessional phagocytes represents a crucial step in the infection process and has likely promoted the evolution of a redundant mechanism and routes of entry. Like many other viral and invasive bacterial pathogens, manipulation of the host cell cytoskeleton represents a focal point in Chlamydia entry. The advent of genetic techniques in C. trachomatis, such as creation of complete gene deletions via fluorescence-reported allelic exchange mutagenesis (FRAEM), is providing important tools to unravel the contributions of bacterial factors in these complex pathways. The type III secretion chaperone Slc1 directs delivery of at least four effectors during the invasion process. Two of these, TarP and TmeA, have been associated with manipulation of actin networks and are essential for normal levels of invasion. The functions of TarP are well established, whereas TmeA is less well characterized. We leverage chlamydial genetics and proximity labeling here to provide evidence that TmeA directly targets host N-WASP to promote Arp2/3-dependent actin polymerization. Our work also shows that TmeA and TarP influence separate, yet synergistic pathways to accomplish chlamydial entry. These data further support an appreciation that a pathogen, confined by a reductionist genome, retains the ability to commit considerable resources to accomplish bottle-neck steps during the infection process. IMPORTANCE The increasing genetic tractability of Chlamydia trachomatis is accelerating the ability to characterize the unique infection biology of this obligate intracellular parasite. These efforts are leading to a greater understanding of the molecular events associated with key virulence requirements. Manipulation of the host actin cytoskeleton plays a pivotal role throughout Chlamydia infection, yet a thorough understanding of the molecular mechanisms initiating and orchestrating actin rearrangements has lagged. Our work highlights the application of genetic manipulation to address open questions regarding chlamydial invasion, a process essential to survival. We provide definitive insight regarding the role of the type III secreted effector TmeA and how that activity relates to another prominent effector, TarP. In addition, our data implicate at least one source that contributes to the functional divergence of entry mechanisms among chlamydial species.

The genus Chlamydia consists of diverse, obligate intracellular bacteria that infect various animals, including humans. Although chlamydial species share many aspects of the typical intracellular lifestyle, such as the biphasic developmental cycle and the preference for invasion of epithelial cells, each chlamydial strain also employs sophisticated species-specific strategies that contribute to an extraordinary diversity in organ and/or tissue tropism and disease manifestation.

Recently, we have witnessed an unprecedented increase in the number of patients suffering from respiratory tract illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The COVID-19 virus is a single-stranded positive-sense RNA virus with a genome size of ~29.9 kb. It is believed that the viral spike (S) protein attaches to angiotensin converting enzyme 2 cell surface receptors and, eventually, the virus gains access into the host cell with the help of intracellular/extracellular proteases or by the endosomal pathway. Once, the virus enters the host cell, it can either be degraded via autophagy or evade autophagic degradation and replicate using the virus encoded RNA dependent RNA polymerase. The virus is highly contagious and can impair the respiratory system of the host causing dyspnea, cough, fever, and tightness in the chest. This disease is also characterized by an abrupt upsurge in the levels of proinflammatory/inflammatory cytokines and chemotactic factors in a process known as cytokine storm. Certain reports have suggested that COVID-19 infection can aggravate cardiovascular complications, in fact, the individuals with underlying co-morbidities are more prone to the disease. In this review, we shall discuss the pathogenesis, clinical manifestations, potential drug candidates, the interaction between virus and autophagy, and the role of coronavirus in exaggerating cardiovascular complications.

Chlamydia trachomatis is an obligate intracellular pathogen that actively promotes invasion of epithelial cells. A virulence-associated type III secretion system contributes to chlamydial entry and at least four effectors have been described that are deployed during this time. Two of these invasion-related effectors, the translocated membrane-associated effectors A and B (TmeA and TmeB), are encoded in a bi-cistronic operon. TmeA directly activates host N-WASP to stimulate Arp2/3-dependent actin polymerization. According to current working models, TmeA-mediated N-WASP activation contributes to invasion. TmeB has not been functionally characterized. Unlike a tmeA null strain, loss of tmeB does not impact invasion efficiency of C. trachomatis. Using strains deficient for multiple genes, we provide evidence that TmeA is dispensable for invasion in the absence of TmeB. Our data indicate that overabundance of TmeB interferes with invasion and that this activity requires active Arp2/3 complex. We further show that TmeB is capable of interfering with Arp2/3-mediated actin polymerization. In aggregate, these data point to opposing functions for TmeA and TmeB that manifest during the invasion process. These studies raise intriguing questions regarding the dynamic interplay between TmeA, TmeB, and branched actin polymerization during chlamydial entry.

Background: Antiretroviral therapy (ART) improves the survival of people living with HIV (PLHIV); however, the rate of cardiovascular disorder and heart failure is significantly increased among the PLHIV. Molecular basis of heart failure in the PLHIV undergoing antiretroviral drug treatment is not clear. The aim of this study is to explore the role of antiretroviral drugs in post translational modification of histones and its epigenetic regulation of gene expression in cardiomyocytes. Methods and Results: Primary rat ventricular cardiomyocytes were treated with a combination of antiretroviral drugs (5 μM of Atazanavir, Abacavir, Ritonavir and Lamivudine) for 4, 12 and 24 hours, and expression of major histone marks playing a role in gene activation (H3K9ac and H3K27ac) and repression (H3K27me3, H3K9me3) were evaluated by western blotting. Our data suggest that treatment with antiretroviral drugs leads to de-acetylation at H3K9ac and H3K27ac, and promotes methylation at H3K27me3 and H3k9me3. Additionally, the expression of epigenetic modifying enzymes was examined by PCR array in cardiomyocytes treated with antiretroviral drugs. PCR array data show that histone deacetylase enzyme Sirt1/2, and methyltransferase enzyme Suv39h1 and Ezh12 were upregulated in drug treated cardiomyocytes. Further, western blot data show that Sirt1, Suv39h1 and Ezh2 protein expression was significantly upregulated in drugs treated cardiomyocytes. Moreover, expression analysis of human cardiac tissue further shows that expression of Sirt1, Suv39h1 and Ezh2 was significantly upregulated in HIV+ patients heart compares to healthy donor. Mechanistically, our data show that expression of epigenetic modifying enzymes was differentially regulated in drug treated cardiomyocytes which may lead to epigenetic modifications of histone proteins. Conclusion: Antiretroviral drug treatment promotes epigenetic alteration in the chromatin which may lead to a change in gene expression of cardiomyocytes. This study may lead to novel therapeutic strategies for the treatment of heart failure in PLWHA.