Syk Associates with Clathrin and Mediates Phosphatidylinositol 3-Kinase Activation during Human Rhinovirus Internalization

Lau, Christine; Wang, Xiaomin; Song, Lihua; North, Michelle L.; Wiehler, Shahina; Chow, Chung‐Wai

doi:10.4049/jimmunol.180.2.870

Cited by 80 publications

(69 citation statements)

References 66 publications

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“…Ezrin is a key component in the clathrin-mediated internalization of rhinovirus (41). After a 12-day treatment of cultured spheroids from human tracheal epithelium with IL-13, levels of ezrin declined by 30% (25), although no change was evident after 7 days (the treatment duration used in the present studies).…”

Section: Discussionmentioning

confidence: 66%

Interleukin-13–Induced Mucous Metaplasia Increases Susceptibility of Human Airway Epithelium to Rhinovirus Infection

Lachowicz-Scroggins¹,

Boushey²,

Finkbeiner³

et al. 2010

Am J Respir Cell Mol Biol

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Infection of airway epithelium by rhinovirus is the most common cause of asthma exacerbations. Even in mild asthma, airway epithelium exhibits mucous metaplasia, which increases with increasing severity of the disease. We previously showed that squamous cultures of human airway epithelium manifest rhinoviral infection at levels many times higher than in well-differentiated cultures of a mucociliary phenotype. Here we tested the hypothesis that mucous metaplasia is also associated with increased levels of rhinoviral infection. Mucous metaplasia was induced with IL-13, which doubled the numbers of goblet cells. In both control (mucociliary) and IL-13-treated (mucous metaplastic) cultures, goblet cells were preferentially infected by rhinovirus. IL-13 doubled the numbers of infected cells by increasing the numbers of infected goblet cells. Furthermore, IL-13 increased both the maturity of goblet cells and the probability that a goblet cell would be infected. The infection of cells other than goblet cells was unaltered by IL-13. Treatment with IL-13 did not alter the levels of rhinovirus receptor ICAM-1, nor did the proliferative effects of IL-13 enhance infection, because rhinovirus did not colocalize with dividing cells. However, the induction of mucous metaplasia caused changes in the apical membrane structure, notably a marked decrease in overall ciliation, and an increase in the overall flatness of the apical surface. We conclude that mucous metaplasia in asthma increases the susceptibility of airway epithelium to infection by rhinovirus because of changes in the overall architecture of the apical surface.Keywords: asthma; interleukin-13; rhinovirus; respiratory tract infection; goblet cells Bronchial responsiveness to viral respiratory infections is heightened in asthma, and most exacerbations of asthma are associated with such infections (1). Rhinovirus is responsible for more than half of all respiratory-tract infections, and is generally thought to be the most common cause of asthma exacerbations (2-5). Rhinovirus infects the airway epithelium, and the airway epithelium is abnormal in asthma. Although evidence for increased epithelial cell exfoliation exists (6), the bestdocumented epithelial change, even in mild asthma, is mucous metaplasia (7,8). We previously showed that the degree of viral infection depends on the type of differentiation of human airway epithelial cell cultures. Specifically, after exposure to the same multiplicity of infection (MOI) of rhinovirus, squamouscell cultures produced z100 times as much virus as cultures of healthy mucociliary phenotype (9). We therefore hypothesized that the mucous metaplasia seen in asthma also makes the epithelium more susceptible to viral infection. To test this hypothesis, we used IL-13 to induce mucous metaplasia in cultures of human airway epithelial cells. We then compared the levels of rhinovirus infection in metaplastic cells and cells of a normal mucociliary phenotype. MATERIALS AND METHODS Human Tissues and Cell CultureEighteen normal, nondiseased...

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Section: Discussionmentioning

confidence: 66%

Interleukin-13–Induced Mucous Metaplasia Increases Susceptibility of Human Airway Epithelium to Rhinovirus Infection

Lachowicz-Scroggins¹,

Boushey²,

Finkbeiner³

et al. 2010

Am J Respir Cell Mol Biol

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“…As expected, over time the total levels of IRS-2 protein increased due to a decrease in proteasomal degradation that is normally promoted by S6K-mediated phosphorylation (33,34). As a direct readout of PI3K activity, we monitored phosphorylation of p85 on Tyr-458, a site that has previously been reported to track with the activation of this enzyme (35,36): rapamycin treatment resulted in an ϳ2.5-fold increase in phosphorylation on Tyr-458 within 16 h (Fig. 2a, p-PI3K p85).…”

Section: Activation Of Pi3k In Cells Lacking Mtorc2mentioning

confidence: 99%

Disruption of the Interface between the Pleckstrin Homology (PH) and Kinase Domains of Akt Protein Is Sufficient for Hydrophobic Motif Site Phosphorylation in the Absence of mTORC2

Warfel

Niederst

Newton

2011

Journal of Biological Chemistry

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The pro-survival kinase Akt requires phosphorylation at two conserved residues, the activation loop site (Thr-308) and the hydrophobic motif site (Ser-473), for maximal activation. Previous reports indicate that mTORC2 is necessary for phosphorylation of the hydrophobic motif and that this site is not phosphorylated in cells lacking components of the mTORC2 complex, such as Sin1. Here The Akt/protein kinase B Ser/Thr protein kinases play a central role in signaling downstream of phosphatidylinositol 3-kinase (PI3K) 2 (1). The three isoforms (Akt1, Akt2, and Akt3) share a similar domain structure: an N-terminal pleckstrin homology (PH) domain, followed by an ␣-helical linker, and a C-terminal kinase domain that is controlled by phosphorylation (2). Once activated by phosphorylation, Akt phosphorylates defined substrates throughout the cell, ultimately inducing pro-proliferation and anti-apoptotic signaling pathways (1). The activation state of Akt is tightly controlled, and its dysregulation is implicated in the development of a variety of diseases, most notably cancer (3).One key regulator of Akt phosphorylation is the mammalian target of rapamycin (mTOR), an evolutionarily conserved Ser/ Thr protein kinase that forms two distinct protein complexes in cells. These complexes are differentially regulated and perform distinct cellular functions (4). The mTOR complex 1 (mTORC1) is composed of mTOR, Raptor, and mLST8 and is sensitive to inhibition by rapamycin. mTORC1 is a crucial regulator of cell growth in response to nutrients, stress, and growth factors (5, 6). A second complex, mTOR complex 2 (mTORC2), consists of mTOR, Rictor, mLST8, and Sin1 and is generally considered to be rapamycin-insensitive (7,8). It is this complex, mTORC2, that regulates Akt and, additionally, protein kinase C (9, 10).Upon biosynthesis, the nascent Akt polypeptide is phosphorylated at the ribosome by mTORC2 (10 -12) at a conserved C-terminal site originally identified in protein kinase C and named the turn motif site (13). Phosphorylation of this residue (Thr-450 in Akt1) (14) is important for the stability of AGC kinases (15,16). Thus, Akt is heavily ubiquitinated and degraded in cells lacking mTORC2 because the turn motif site is not phosphorylated (10, 11). This processing phosphorylation of Akt is constitutive and its dephosphorylation in cells has not been reported.Once processed by phosphorylation at the turn motif site, Akt localizes to the cytosol, where it is maintained in an inactive conformation through the interaction between its PH and kinase domains (17). In the presence of proliferative signals, PI3K is activated and generates the lipid second messenger phosphatidylinositol 3,4,5-trisphosphate (PIP 3 ). Akt is subsequently recruited from the cytosol to the plasma membrane through binding of its PH domain to PIP 3 , resulting in a conformational change that separates the PH and kinase domains and unmasks two key regulatory residues whose phosphorylations are required for maximal activation of the kinase. The first site,...

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“…For example, epithelial edema and shedding together with mucus production can cause airway obstruction and wheezing. In addition, viral replication initiates innate immune responses within the epithelial cell, including induction of interferons, antiviral effectors, and chemokines that recruit inflammatory cells into the airway (22,55,63,93,117). There is evidence that HRV, like many other viruses, has developed mechanisms to inhibit antiviral responses by cleaving proteins such as RIG-I and IPS-1 that are involved in virus recognition pathways (3,17).…”

Section: Hrv Pathogenesismentioning

confidence: 99%

The ABCs of Rhinoviruses, Wheezing, and Asthma

Gern

2010

J Virol

235

226

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Human rhinoviruses (HRVs) were discovered as common cold pathogens over 50 years ago. Recent advances in molecular viral diagnostics have led to an appreciation of their role in more-significant respiratory illnesses, including bronchiolitis in infancy, childhood pneumonia, and acute exacerbations of chronic respiratory diseases such as asthma, chronic obstructive lung disease, and cystic fibrosis. Until a few years ago, only two groups of HRVs (A and B) had been recognized. However, full and partial sequencing of HRVs led to the discovery of a third species of HRV (HRV-C) that has distinct structural and biologic features. Risk factors and pathogenic mechanisms for more-severe HRV infections are being defined, and yet fundamental questions persist about mechanisms relating this common pathogen to allergic diseases and asthma. The close relationship between HRV infections and asthma suggests that antiviral treatments could have a major impact on the morbidity associated with this chronic respiratory disease.Virology and clinical textbooks and virtually all web-based information sources generally describe human rhinoviruses (HRVs) as the most frequent cause of the common cold. In this light, HRVs are important pathogens because common colds are so widespread and annoying, and from an economic perspective, supplying symptomatic-relief medications is a huge industry. A 2003 study estimated that expenditures on common cold medications in the United States exceeded 4 billion dollars, including 1.1 billion dollars spent on inappropriate prescriptions for antibiotics (18). Finding a cure for the common cold has been a much-publicized goal ever since HRVs were first discovered in the 1950s and 1960s. The basic biology of the replication cycle was soon described, and most HRVs were found to replicate best at 33°to 35°C (88, 99), which is consistent with their role as upper airway pathogens. HRVs were found to have tremendous diversity, and approximately 100 serotypes in two groups (A and B) had been identified by 1990, when it was presumed that all, or nearly all, HRVs had been identified. These HRVs were found to bind to one of two main receptors: ICAM-1 (major group) (30) and the low-density-lipoprotein receptor (most of the minor group) (35). Despite advances in understanding HRV genetics and the picornavirus replication cycle, efforts toward developing specific antivirals have fallen short due to modest efficacy, side effects, drug interactions, and economic considerations (16). Consequently, enthusiasm for pursuing a common cold cure has waned, and the pharmaceutical industry has refocused attention on viruses that cause more-significant illnesses. This failure is a bit embarrassing. As summarized by White and Fenner, "In this era of organ transplantation, genetic engineering, and other dramatic demonstrations of the wonders of medical science, the man in the street perceives a certain irony in the inability of modern medicine to make the slightest impact on that most trivial of all human ailments, the common cold" ...

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Syk Associates with Clathrin and Mediates Phosphatidylinositol 3-Kinase Activation during Human Rhinovirus Internalization

Cited by 80 publications

References 66 publications

Interleukin-13–Induced Mucous Metaplasia Increases Susceptibility of Human Airway Epithelium to Rhinovirus Infection

Interleukin-13–Induced Mucous Metaplasia Increases Susceptibility of Human Airway Epithelium to Rhinovirus Infection

Disruption of the Interface between the Pleckstrin Homology (PH) and Kinase Domains of Akt Protein Is Sufficient for Hydrophobic Motif Site Phosphorylation in the Absence of mTORC2

The ABCs of Rhinoviruses, Wheezing, and Asthma

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