Neuraminidase of Influenza A Virus Binds Lysosome-Associated Membrane Proteins Directly and Induces Lysosome Rupture

Abstract

As a recycling center, lysosomes are filled with numerous acid hydrolase enzymes that break down waste materials and invading pathogens. Recently, lysosomal cell death has been defined as "lysosomal membrane permeabilization and the consequent leakage of lysosome contents into cytosol." Here, we show that the neuraminidase (NA) of H5N1 influenza A virus markedly deglycosylates and degrades lysosome-associated membrane proteins (LAMPs; the most abundant membrane proteins of lysosome), which induces lysosomal rupture, and finally leads to cell death of alveolar epithelial carcinoma A549 cells and human tracheal epithelial cells. The NA inhibitors peramivir and zanamivir could effectively block the deglycosylation of LAMPs, inhibit the virus cell entry, and prevent cell death induced by the H5N1 influenza virus. The NA of seasonal H1N1 virus, however, does not share these characteristics. Our findings not only reveal a novel role of NA in the early stage of the H5N1 influenza virus life cycle but also elucidate the molecular mechanism of lysosomal rupture crucial for influenza virus induced cell death. IMPORTANCEThe integrity of lysosomes is vital for maintaining cell homeostasis, cellular defense and clearance of invading pathogens. This study shows that the H5N1 influenza virus could induce lysosomal rupture through deglycosylating lysosome-associated membrane proteins (LAMPs) mediated by the neuraminidase activity of NA protein. NA inhibitors such as peramivir and zanamivir could inhibit the deglycosylation of LAMPs and protect lysosomes, which also further interferes with the H5N1 influenza virus infection at early stage of life cycle. This work is significant because it presents new concepts for NA's function, as well as for influenza inhibitors' mechanism of action, and could partially explain the high mortality and high viral load after H5N1 virus infection in human beings and why NA inhibitors have more potent therapeutic effects for lethal avian influenza virus infections at early stage.

Autophagy is involved in regulating the immune response of dendritic cells to influenza A (H1N1) pdm09 infection

“…Hepatitis B virus and influenza A virus have been reported to resist lysosome-mediated degradation. 41,42 It may also be the case that H1N1 viruses are resistant to lysosome-mediated degradation. Moreover, lysosomes may shelter H1N1 virus from clearance by the host cell defence system.…”

Influenza A virus hemagglutinin and neuraminidase act as novel motile machinery

“…NA inhibitors such as zanamivir and oseltamivir suppress virus infection262728. Our observation of NA-dependent IAV movement on cells implies that virus movement contributes to endocytosis of IAVs.…”

“…Nevertheless, NA inhibitors reportedly suppress virus infection, indicating a major role of NA in infection262728. However, the specifics of this functional role remained unclear.…”

Lysosomes in programmed cell death pathways: from initiators to amplifiers

“…Also several other toxins, such as tetanus, botulinum an anthrax toxin, nigericin, leukotoxin, mycotoxins, venom toxins from cobra and rattlesnake, have been associated with LMP. On the other hand, viral proteins can initiate LMP by generating lysosomal membrane rupture, pore formation, membrane curvature stress or vesicular swelling or even by detergent-like activity (Tosteson and Chow, 1997;Fuchs and Blaas, 2010;Johansson et al, 2010;Maier et al, 2010;Aits and Jaattela, 2013;Jiang and Mizushima, 2014;Ju et al, 2015). In addition, proapoptotic Bcl2 family members Bax and Bak that are primarily involved in mitochondrial membrane permeabilization, and Bid, were also suggested to be involved in triggering LMP (Johansson et al, 2010).…”