The Unfolded Protein Response: A Key Player in Zika Virus-Associated Congenital Microcephaly

Zika virus (ZIKV) is a mosquito-borne virus that belongs to the Flaviviridae family, together with dengue, yellow fever, and West Nile viruses. In the wake of its emergence in the French Polynesia and in the Americas, ZIKV has been shown to cause congenital microcephaly. It is the first arbovirus which has been proven to be teratogenic and sexually transmissible. Confronted with this major public health challenge, the scientific and medical communities teamed up to precisely characterize the clinical features of congenital ZIKV syndrome and its underlying pathophysiological mechanisms. This review focuses on the critical impact of the unfolded protein response (UPR) on ZIKV-associated congenital microcephaly. ZIKV infection of cortical neuron progenitors leads to high endoplasmic reticulum (ER) stress. This results in both the stalling of indirect neurogenesis, and UPR-dependent neuronal apoptotic death, and leads to cortical microcephaly. In line with these results, the administration of molecules inhibiting UPR prevents ZIKV-induced cortical microcephaly. The discovery of the link between ZIKV infection and UPR activation has a broader relevance, since this pathway plays a crucial role in many distinct cellular processes and its induction by ZIKV may account for several reported ZIKV-associated defects

Structural Stability of Human Protein Tyrosine Phosphatase ρ Catalytic Domain: Effect of Point Mutations

Protein tyrosine phosphatase ρ (PTPρ) belongs to the classical receptor type IIB family of protein tyrosine phosphatase, the most frequently mutated tyrosine phosphatase in human cancer. There are evidences to suggest that PTPρ may act as a tumor suppressor gene and dysregulation of Tyr phosphorylation can be observed in diverse diseases, such as diabetes, immune deficiencies and cancer. PTPρ variants in the catalytic domain have been identified in cancer tissues. These natural variants are nonsynonymous single nucleotide polymorphisms, variations of a single nucleotide occurring in the coding region and leading to amino acid substitutions. In this study we investigated the effect of amino acid substitution on the structural stability and on the activity of the membrane-proximal catalytic domain of PTPρ. We expressed and purified as soluble recombinant proteins some of the mutants of the membrane-proximal catalytic domain of PTPρ identified in colorectal cancer and in the single nucleotide polymorphisms database. The mutants show a decreased thermal and thermodynamic stability and decreased activation energy relative to phosphatase activity, when compared to wild- type. All the variants show three-state equilibrium unfolding transitions similar to that of the wild- type, with the accumulation of a folding intermediate populated at ∼4.0 M urea

Contrasting Roles for TLR Ligands in HIV-1 Pathogenesis

The first line of a host's response to various pathogens is triggered by their engagement of cellular pattern recognition receptors (PRRs). Binding of microbial ligands to these receptors leads to the induction of a variety of cellular factors that alter intracellular and extracellular environment and interfere directly or indirectly with the life cycle of the triggering pathogen. Such changes may also affect any coinfecting microbe. Using ligands to Toll-like receptors (TLRs) 5 and 9, we examined their effect on human immunodeficiency virus (HIV)-1 replication in lymphoid tissue ex vivo. We found marked differences in the outcomes of such treatment. While flagellin (TLR5 agonist) treatment enhanced replication of CC chemokine receptor 5 (CCR 5)-tropic and CXC chemokine receptor 4 (CXCR4)-tropic HIV-1, treatment with oligodeoxynucleotide (ODN) M362 (TLR9 agonist) suppressed both viral variants. The differential effects of these TLR ligands on HIV-1 replication correlated with changes in production of CC chemokines CCL3, CCL4, CCL5, and of CXC chemokines CXCL10, and CXCL12 in the ligand-treated HIV-1-infected tissues. The nature and/or magnitude of these changes were dependent on the ligand as well as on the HIV-1 viral strain. Moreover, the tested ligands differed in their ability to induce cellular activation as evaluated by the expression of the cluster of differentiation markers (CD) 25, CD38, CD39, CD69, CD154, and human leukocyte antigen D related (HLA)-DR as well as of a cell proliferation marker, Ki67, and of CCR5. No significant effect of the ligand treatment was observed on apoptosis and cell death/loss in the treated lymphoid tissue ex vivo. Our results suggest that binding of microbial ligands to TLRs is one of the mechanisms that mediate interactions between coinfected microbes and HIV-1 in human tissues. Thus, the engagement of appropriate TLRs by microbial molecules or their mimetic might become a new strategy for HIV therapy or prevention

The Unfolded Protein Response: A Key Player in Zika Virus-Associated Congenital Microcephaly

International audienceZika virus (ZIKV) is a mosquito-borne virus that belongs to the Flaviviridae family, together with dengue, yellow fever, and West Nile viruses. In the wake of its emergence in the French Polynesia and in the Americas, ZIKV has been shown to cause congenital microcephaly. It is the first arbovirus which has been proven to be teratogenic and sexually transmissible. Confronted with this major public health challenge, the scientific and medical communities teamed up to precisely characterize the clinical features of congenital ZIKV syndrome and its underlying pathophysiological mechanisms. This review focuses on the critical impact of the unfolded protein response (UPR) on ZIKV-associated congenital microcephaly. ZIKV infection of cortical neuron progenitors leads to high endoplasmic reticulum (ER) stress. This results in both the stalling of indirect neurogenesis, and UPR-dependent neuronal apoptotic death, and leads to cortical microcephaly. In line with these results, the administration of molecules inhibiting UPR prevents ZIKV-induced cortical microcephaly. The discovery of the link between ZIKV infection and UPR activation has a broader relevance, since this pathway plays a crucial role in many distinct cellular processes and its induction by ZIKV may account for several reported ZIKV-associated defects

Location of PTPρ mutations.

<p>(<b>A</b>) Structure of PTPρ (PDB code 2OOQ) shown as a ribbon diagram. Mutated residues are highlighted in ball and stick and transparent cpk representation and are labelled in red. The active site cystein residue (C1106) is also shown and the catalytically important WPD loop is coloured in yellow. (<b>B</b>) Local environment of N1128. (<b>C</b>) Local environment of D927.</p

Spectroscopic properties of PTPρ wild-type and mutants.

<p>(<b>A</b>) Near-UV CD spectra were recorded in a 1-cm quartz cuvette at 1.0 mg/ml protein concentration in 20 mM Tris/HCl, pH 7.5 containing 0.2 M NaCl and 2 mM DTT. (<b>B</b>) Intrinsic fluorescence emission spectra were recorded at 0.04 mg/ml protein concentration (295 nm excitation wavelength) in 20 mM Tris/HCl, pH 7.5 containing 0.2 M NaCl and 200 µM DTT. (<b>C</b>) Far-UV CD spectra were recorded in a 0.1-cm quartz cuvette at 0.2 mg/ml in 20 mM Tris/HCl, pH 7.5 containing 0.2 M NaCl and 0.4 mM DTT.</p

Intrinsic fluorescence emission spectra of PTPρ wild-type and mutants.

<p>Fluorescence spectra of PTPρ wild-type and mutants in 0 M (continuous lines), 8.30 M (dotted lines), 3.95 M (D927G and N1128I, dashed lines) and 4.45 M urea (wild-type and Q987K, dashed lines) were recorded at 0.04 mg/ml protein concentration (295 nm excitation wavelength) at 10°C in 20 mM Tris/HCl, pH 7.5 containing 0.2 M NaCl and 200 µM DTT.</p

Primers sequences for mutagenesis of PTPρ.

<p>Mutations were introduced using a Quick Change Site-Directed Mutagenesis Kit (Stratagene) with the listed primers.</p

Thermal transition of PTPρ wild-type and mutants.

<p>(<b>A</b>) PTPρ wild-type, N1128I, Q987K and D927G were heated from 10°C to 72°C in a 0.1-cm quartz cuvette at 0.2 mg/ml in 20 mM Tris/HCl, pH 7.5 containing 0.2 M NaCl and 0.4 mM DTT. The dichroic activity at 209 nm was monitored continuously every 0.5°C. The inset shows the first derivative of the same data. (<b>B</b>) PMTV data recorded in the same experiments shown in (<b>A</b>).</p