Biology subjects

Lee, C. Y.

Publications and source records attributed to Lee, C. Y..

23 records · Page 2Linked to original sources

bioRxiv2020

Bivalent binding of a fully human IgG to the SARS-CoV-2 spike proteins reveals mechanisms of potent neutralization

In vitro antibody selection against pathogens from naive combinatorial libraries can yield various classes of antigen-specific binders that are distinct from those evolved from natural infection1-4. Also, rapid neutralizing antibody discovery can be made possible by a strategy that selects for those interfering with pathogen and host interaction5. Here we report the discovery of antibodies that neutralize SARS-CoV-2, the virus responsible for the COVID-19 pandemic, from a highly diverse naive human Fab library. Lead antibody 5A6 blocks the receptor binding domain (RBD) of the viral spike from binding to the host receptor angiotensin converting enzyme 2 (ACE2), neutralizes SARS-CoV-2 infection of Vero E6 cells, and reduces viral replication in reconstituted human nasal and bronchial epithelium models. 5A6 has a high occupancy on the viral surface and exerts its neutralization activity via a bivalent binding mode to the tip of two neighbouring RBDs at the ACE2 interaction interface, one in the "up" and the other in the "down" position, explaining its superior neutralization capacity. Furthermore, 5A6 is insensitive to several spike mutations identified in clinical isolates, including the D614G mutant that has become dominant worldwide. Our results suggest that 5A6 could be an effective prophylactic and therapeutic treatment of COVID-19.

microbiology↗

bioRxiv2020

Local and global dichotomic dysfunction in resting and evoked functional connectivity precedes tauopathy

Functional network activity alterations are one of the earliest hallmarks of Alzheimers disease (AD), detected prior to amyloidosis and tauopathy. Better understanding the neuronal underpinnings of such network alterations could offer mechanistic insight into AD progression. Here, we examined a mouse model (early-tauopathy 3xTgAD mice) recapitulating this early AD stage. We found resting functional connectivity loss within ventral networks, including the entorhinal cortex, aligning with the spatial distribution of tauopathy reported in humans. Unexpectedly, in contrast to decreased connectivity at rest, 3xTgAD mice show enhanced fMRI signal within several projection areas following optogenetic activation of the entorhinal cortex. We corroborate this finding by demonstrating neuronal facilitation within ventral networks and synaptic hyperexcitability in projection targets. 3xTgAD mice thus reveal a dichotomic hypo-connected resting/hyper-responsive active phenotype. The strong homotopy between the areas affected supports the translatability of this pathophysiological model to tau-related deficits in humans.

neuroscience↗

bioRxiv2019

Sporadic activation of an oxidative stress-dependent NRF2-p53 signaling network in breast epithelial spheroids and premalignancies

Breast-mammary epithelial cells experience different local environments during tissue development and tumorigenesis. Microenvironmental heterogeneity gives rise to distinct cell-regulatory states whose identity and importance are just beginning to be appreciated. Cellular states diversify when clonal 3D spheroids are cultured in basement membrane, and prior transcriptomic analyses identified a state associated with stress tolerance and poor response to anticancer therapeutics. Here, we examined the regulation of this state and found that it is jointly coordinated by the NRF2 and p53 pathways, which are co-stabilized by spontaneous oxidative stress within the 3D cultures. Inhibition of NRF2 or p53 individually disrupts some of the transcripts defining the regulatory state but does not yield a notable phenotype in nontransformed breast epithelial cells. In contrast, combined perturbation prevents 3D growth in an oxidative stress-dependent manner. By integrating systems models of NRF2 and p53 signaling together as a single oxidative-stress network, we recapitulate these observations and make predictions about oxidative stress profiles during 3D growth. Similar coordination of NRF2 and p53 signaling is observed in normal breast epithelial tissue and hormone-negative ductal carcinoma in situ lesions. However, the pathways are uncoupled in triple-negative breast cancer, a subtype in which p53 is usually mutated. Using the integrated model, we reconcile the different NRF2-knockdown phenotypes of triple-negative cancer lines with their inferred handling of oxidative stress. Our results point to an oxidative stress-tolerance network that is important for single cells during glandular development and the early stages of breast cancer. One Sentence SummaryReactive oxygen species co-stabilize a non-oncogene and a tumor suppressor for triple-negative breast cancer when cells are surrounded by basement-membrane ECM.

cancer biology↗

bioRxiv2019

Metastatic function of METTL18 in breast cancer via actin methylation and Src

Recently, a SET domain containing 3 (SETD3) was identified as an actin histidine methyltransferase, functioning to control replication and pathogenesis in multiple mouse models for enterovirus infection as well as the regulation of smooth muscle contractility linked to primary dystocia. Here, in this study, we report another type of actin histidine methyltransferase, METTL18, that regulates the metastatic potential of breast cancer in human. Among methyltransferases, METTL18 was highly amplified in human breast cancer. In particular, poor prognosis was associated with high expression of METTL18 in HER2-negative breast cancer patients. This gene product was also found to be a critical component of metastatic responses. Loss of METTL18 expression significantly reduced metastatic responses of breast tumor cells both in vitro and in vivo. Mechanistically, it was observed that METTL18 increased actin polymerization, upregulated complex formation with HSP90AA1 and Src, enhanced the activity of an intermediate form of Src with tyrosine phosphorylation at both Y416 and Y527, and induced cellular metastatic responses, including morphological change, migration, and invasion of MDA-MB-231 cells in vitro and in mice. Methylated actin at His73 served as a critical site for interaction with HSP90AA1 and Src to activate p85/PI3K and STAT3. Our findings suggest that METTL18 plays critical roles in metastatic responses of HER2-negative breast cancer cells via actin polymerization and the generation of an intermediate form of Src.

cancer biology↗

bioRxiv2017

Zika virus infection preferentially counterbalances human peripheral monocyte and/or NK-cell activity

Zika virus (ZIKV) has re-emerged in the population and caused unprecedented global outbreaks. Here, the transcriptomic consequences of ZIKV infection were studied systematically firstly in human peripheral blood CD14+ monocytes and monocyte-derived macrophages with high density RNA-sequencing. Analyses of the ZIKV genome revealed that the virus underwent genetic diversification and differential mRNA abundance was found in host cells during infection. Notably, there was a significant change in the cellular response with crosstalk between monocytes and natural killer (NK) cells as one of the highly identified pathway. Immune-phenotyping of peripheral blood from ZIKV-infected patients further confirmed the activation of NK cells during acute infection. ZIKV infection in peripheral blood cells isolated from healthy donors led to the induction of IFN{gamma} and CD107a -- two key markers of NK-cell function. Depletion of CD14+ monocytes from peripheral blood resulted in a reduction of these markers and reduced priming of NK cells during infection. This was complemented by the immunoproteomic changes observed. Mechanistically, ZIKV infection preferentially counterbalances monocyte and/or NK-cell activity, with implications for targeted cytokine immunotherapies.

immunology↗