A molecular simulation study of the clinical G409V mutant in PINK1 associated with early-onset Parkinson's disease.

The serine/threonine kinase PINK1 is responsible for phosphorylating a ubiquitin (Ub)-like domain in an E3 Ub ligase Parkin protein and a Parkin-bound Ub. PINK1 works as a mitochondrial quality control by phosphorylating and activating the E3 ubiquitin ligase Parkin. Recent medicinal study has reported that mutations of Parkin and PINK1 cause defects in mitophagy and induce early-onset Parkinson's disease (EOPD). In this study, we conducted molecular dynamics simulations to investigate the structural discrepancy caused by a clinical G409V mutation in PINK1 kinase domain's A-loop. The Ub phosphorylation begins with PINK1 D362 deprotonating the hydroxyl group of the substrate Ub's S65' and PINK1's A-loop is responsible for coordinating S65'. On contrary to G409 offering structural plasticity, the replaced, bulky V409 interferes with the alignment of D362-S65', seriously hampering Ub phosphorylation, leading to the accumulation of damaged mitochondria, and ultimately EOPD. In this study, we predicted the hPINK1WT-UbWT binding mode and detected the structural impact brought by G409V replacement. It is expected the concluded remarks to be beneficial for developing cures to alleviate structural interference and restore PINK1 function.

Effect of interferon receptor 1 silenced human diploid MRC⁃5 cell line on replication of varicella⁃zoster virus / 中国生物制品学杂志

@#Abstract：Objective To improve the replication level of varicella⁃zoster virus（VZV）in human diploid cell line MRC⁃5 and increase the yield of VZV vaccine by reducing the expression of interferon（IFN）related genes via optimizing the cell line MRC⁃5. Methods Interferon receptor 1（IFNAR1）silenced MRC⁃5 cell line（MRC⁃5IFNAR1⁃）was constructed by CRISPR／Cas9 gene editing technology，which was determined for the relative expression of IFNAR1 mRNA，and for those of mRNA of IFN related genes IFNβ and OAS1 after VZV infection by qRT⁃PCR to evaluate the effect of gene silencing. Gene mutation sequences were further identified by sequencing of the silenced sites. The replication of VZV in MRC⁃5 and MRC⁃5IFNAR1⁃ cell lines was compared 168 h after VZV infection by using qRT⁃PCR and plaque formation unit（PFU）assay， to evaluate the effect of MRC⁃5IFNAR1⁃cell line on VZV replication. Results The growth status of MRC⁃5IFNAR1⁃ cell line wasconsistent with that of MRC ⁃ 5 cells，and the relative expression of IFNAR1 mRNA decreased by 73%；The relative expressions of IFNβ and OAS1 mRNA in MRC⁃5IFNAR1⁃ cell line were 61% and 90% lower than those in MRC⁃ 5 cells respectively after VZV infection；In addition，168 h after VZV infection，the level of DNA replication and the titer of VZV increased by 5. 7 folds and 4 folds respectively. Conclusion The successful establishment of MRC⁃5IFNAR1⁃ cell line may be a potential scheme to increase the yield of vaccines based on human diploid cells，and provided a reference for expanding production of VZV vaccine.

Molecular Modeling for Structural Insights Concerning the Activation Mechanisms of F1174L and R1275Q Mutations on Anaplastic Lymphoma Kinase.

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase involved in various cancers. In its basal state, the structure of ALK is in an autoinhibitory form stabilized by its A-loop, which runs from the N-lobe to the C-lobe of the kinase. Specifically, the A-loop adopts an inhibitory pose with its proximal A-loop helix (αAL-helix) to anchor the αC-helix orientation in an inactive form in the N-lobe; the distal portion of the A-loop is packed against the C-lobe to block the peptide substrate from binding. Upon phosphorylation of the first A-loop tyrosine (Y1278), the αAL-helix unfolds; the distal A-loop detaches from the C-lobe and reveals the P+1 pocket that accommodates the residues immediately after their phosphorylation, and ALK is activated accordingly. Recently, two neuroblastoma mutants, F1174L and R1275Q, have been determined to cause ALK activation without phosphorylation on Y1278. Notably, F1174 is located on the C-terminus of the αC-helix and away from the A-loop, whereas R1275 sits on the αAL-helix. In this molecular modeling study, we investigated the structural impacts of F1174L and R1275Q that lead to the gain-of-function event. Wild-type ALK and ALK with phosphorylated Y1278 were also modeled for comparison. Our modeling suggests that the replacement of F1174 with a smaller residue, namely leucine, moves the αC-helix and αAL-helix into closer contact and further distorts the distal portion of the A-loop. In wild-type ALK, R1275 assumes the dual role of maintaining the αAL-helix⁻αC-helix interaction in an inactive form and securing αAL-helix conformation through the D1276⁻R1275 interaction. Accordingly, mutating R1275 to a glutamine reorients the αC-helix to an active form and deforms the entire A-loop. In both F1174L and R1275Q mutants, the A-loop rearranges itself to expose the P+1 pocket, and kinase activity resumes.