Caveolin 1 restricts Group A Streptococcus invasion of nonphagocytic host cells

A brief review on Group A Streptococcus pathogenesis and vaccine development

Streptococcus pyogenes, also known as Group A Streptococcus (GAS), is a Gram-positive human-exclusive pathogen, responsible for more than 500 000 deaths annually worldwide. Upon infection, GAS commonly triggers mild symptoms such as pharyngitis, pyoderma and fever. However, recurrent infections or prolonged exposure to GAS might lead to life-threatening conditions. Necrotizing fasciitis, streptococcal toxic shock syndrome and post-immune mediated diseases, such as poststreptococcal glomerulonephritis, acute rheumatic fever and rheumatic heart disease, contribute to very high mortality rates in non-industrialized countries. Though an initial reduction in GAS infections was observed in high-income countries, global outbreaks of GAS, causing rheumatic fever and acute poststreptococcal glomerulonephritis, have been reported over the last decade. At the same time, our understanding of GAS pathogenesis and transmission has vastly increased, with detailed insight into the various stages of infection, beginning with adhesion, colonization and evasion of the host immune system. Despite deeper knowledge of the impact of GAS on the human body, the development of a successful vaccine for prophylaxis of GAS remains outstanding. In this review, we discuss the challenges involved in identifying a universal GAS vaccine and describe several potential vaccine candidates that we believe warrant pursuit.

Caveolin-1 as a possible target in the treatment for acne

Expression of caveolin-1 (Cav-1) is an important pathophysiological factor in acne. Cav-1 strongly interacts with such well-recognized etiopathogenic factors such as hyperseborrhea, follicular hyperkeratinization and pathogenicity of Cutibacterium acnes. Cav-1 is a strong negative regulator of transforming growth factor beta (TGF-β) expression. It acts as a critical determinant of autophagy, which is significantly induced in acne lesions through C. acnes and by absorption of fatty acids. Cav-1 also demonstrates different correlations with the development of innate immunity. We propose that normalization of Cav-1 expression can serve as a target in anti-acne therapy.

Group A Streptococcus NAD-Glycohydrolase Inhibits Caveolin 1-Mediated Internalization Into Human Epithelial Cells

Group A Streptococcus (GAS) invades epithelial cells causing persistent infection. GAS has a variety of effector proteins that modulate host systems to affect their survival in host environments. The main effector proteins of GAS are NAD-glycohydrolase (Nga) and streptolysin O (SLO). Although Nga has NADase activity and shows SLO-dependent cytotoxicity, some clinical isolates harbor NADase-inactive subtypes of Nga, and the function of NADase-inactive Nga is still unclear. In this study, we found that deletion of nga enhanced the internalization of GAS into HeLa and Ca9-22 cells. Amino acid substitution of Nga R289K/G330D (NADase-inactive) does not enhance GAS invasion, suggesting that Nga may inhibit the internalization of GAS into host cells in an NADase-independent manner. Moreover, double deletion of slo and nga showed similar invasion percentages compared with wild-type GAS, indicating the important role of SLO in the inhibition of GAS invasion by Nga. Furthermore, enhanced internalization of the nga deletion mutant was not observed in Cav1-knockout HeLa cells. Altogether, these findings demonstrate an unrecognized NADase-independent function of Nga as a negative regulator of CAV1-mediated internalization into epithelial cells.

Caveolae: Structure, Function, and Relationship to Disease

The plasma membrane of eukaryotic cells is not a simple sheet of lipids and proteins but is differentiated into subdomains with crucial functions. Caveolae, small pits in the plasma membrane, are the most abundant surface subdomains of many mammalian cells. The cellular functions of caveolae have long remained obscure, but a new molecular understanding of caveola formation has led to insights into their workings. Caveolae are formed by the coordinated action of a number of lipid-interacting proteins to produce a microdomain with a specific structure and lipid composition. Caveolae can bud from the plasma membrane to form an endocytic vesicle or can flatten into the membrane to help cells withstand mechanical stress. The role of caveolae as mechanoprotective and signal transduction elements is reviewed in the context of disease conditions associated with caveola dysfunction.