Kumar, N. K. | bioRxiv Science

bioRxiv2020

Megakaryopoiesis in Dengue virus infected K562 cell promotes viral replication which inhibits endomitosis and accumulation of ROS associated with differentiation

In the human host blood Monocytes and bone marrow Megakaryocytes are implicated as major sites supporting high replication. The human K562 cell line supports DENV replication and represent Megakaryocyte-Erythrocyte progenitors (MEP), replicating features of in vivo Megakaryopoiesis upon stimulation with Phorbol esters. In this article, we report results that indicate the mutual influence of Megakaryopoiesis and DENV replication on each other, through comparison of PMA-induced differentiation of either mock-infected or DENV-infected K562 cells. We present data showing PMA-induced differentiation to drastically increase DENV replication and a concomitant augmented secretion of infectious virus. Although the mechanism is not clear yet, we show that it is not through an increased uptake of virus by differentiated cells. On the other hand, DENV replication in cells undergoing PMA-induced differentiation, interferes with major differentiation markers of Megakaryopoiesis including activation of ERK1/2 MAP Kinase, endomitosis and surface expression of platelet-specific proteins without any drastic effect on cell death. Among signaling intermediaries of the JAK-STAT pathway, we observed infection associated degradation of SOC3 protein similar to earlier observations with STAT2. DENV infection leads to accumulation of Reactive-oxygen species (ROS) in different cells including K562. PMA-induced differentiation of uninfected K562 cells also leads to intracellular ROS accumulation. Interestingly, we observed ROS accumulation to be suppressed by concomitant DENV replication in K562 cells undergoing PMA-induced differentiation. This is the first report of a model system where DENV replication suppresses intracellular ROS accumulation. The implications of these results for Megakaryopoiesis and viral replication would be discussed.Competing Interest StatementThe authors have declared no competing interest.View Full Text

microbiology↗

bioRxiv2020

Hilbert space filling curves for interpretable point mutation effects on peptide conformational dynamics

Spontaneous self-organization of solid-binding peptides on single-layer atomic materials offers enormous potential in employing these systems for practical technological and medical applications. Molecular self-organization of peptides depends highly on their sequences which, in turn, affect their conformational behavior under aqueous conditions. Traditional ways of computationally studying the effect of mutations on the conformation states involves dimension reduction on cosine and sine transformed torsion angles, often represented as Ramachandran plots. Although these studies successfully cluster conformation states, they fail to intuitively characterize the effect of the point mutation(s) directly, necessitating further data analysis. Here, we apply Hilbert Space-Filling-Curve (HSFC) on the torsion angles and demonstrate intuitive visualization for the effect of point mutations on conformation states and secondary structure dynamics along a reaction coordinate. We perform molecular dynamics (MD) simulation on wild-type graphene binding peptide (WT-GrBP5). The 12-amino acid long peptide was selected by directed evolution and known to self-organize on atomically flat surface of graphene only under low-neutral pH at room temperature. A charge neutral mutant, M9-GrBP5, on the other hand, assembles at a broader range of pHs at room temperature, as expected. The HSFC shows clearly that the mutated amino acids in M9 do not correlate with the reaction coordinate of pH change, unlike that of WT, confirming heuristic knowledge. Understanding the effect of specific amino acid {varphi}-{psi} pairs that contribute most to the changes in the conformational space of the peptide with changing conditions, will help in analyzing effects of point mutations in peptide sequences. The knowledge of the conformational behavior of solid binding peptides, in general, and its effect on their self-organization propensities on solid surfaces would lead to the rational design of sequences that form soft bio/nano hybrid interfaces in the future towards robust strategies for surface biofunctionalization, in general, and bioelectronics and biosensors, in particular.

biophysics↗