Biology subjects

Martinek, J.

Publications and source records attributed to Martinek, J..

3 recordsLinked to original sources

bioRxiv2023

Spatiotemporally organized immunomodulatory response to SARS-CoV-2 virus in primary human broncho-alveolar epithelia

The COVID-19 pandemic continues to be a health crisis with major unmet medical needs. The early responses from airway epithelial cells, the first target of the virus regulating the progression towards severe disease, are not fully understood. Primary human air-liquid interface cultures representing the broncho-alveolar epithelia were used to study the kinetics and dynamics of SARS-CoV-2 variants infection. The infection measured by nucleoprotein expression, was a late event appearing between day 4-6 post infection for Wuhan-like virus. Other variants demonstrated increasingly accelerated timelines of infection. All variants triggered similar transcriptional signatures, an "early" inflammatory/immune signature preceding a "late" type I/III IFN, but differences in the quality and kinetics were found, consistent with the timing of nucleoprotein expression. Response to virus was spatially organized: CSF3 expression in basal cells and CCL20 in apical cells. Thus, SARS-CoV-2 virus triggers specific responses modulated over time to engage different arms of immune response.

immunology↗

bioRxiv2022

Autologous humanized PDX modeling for immuno-oncology recapitulates the human tumor microenvironment

Interactions between immune and tumor cells are critical to determining cancer progression and response. In addition, preclinical prediction of immune-related drug efficacy is limited by inter-species differences between human and mouse, as well as inter-person germline and somatic variation. Here we develop an autologous system that models the TME in individual patients. With patient-derived bone marrow, we engrafted a patients hematopoietic system in MISTRG6 mice followed by patient-derived xenograft (PDX) tissue, providing a genetically matched autologous model. We used this system to prospectively study tumor-immune interactions in solid tumor patients. Autologous PDX mice generated innate and adaptive immune populations; these cells populated the TME; and tumors from autologously engrafted mice grew larger than tumors from non-engrafted littermate controls. Single-cell transcriptomics revealed a prominent VEGF-A signature in TME myeloid cells, and inhibition of human VEGF-A abrogated enhanced growth, demonstrating the utility of the autologous PDX system for pre-clinical testing.

cancer biology↗

bioRxiv2022

ARP2/3 complex associates with peroxisomes to participate in pexophagy in plants

ARP2/3 is a heteroheptameric protein complex evolutionary conserved in all eukaryotic organisms. Its conserved role is based on the induction of actin polymerization at the interface between membranes and the cytoplasm. Plant ARP2/3 has been reported to participate in actin reorganization at the plasma membrane during polarized growth of trichomes and at the plasma membrane-endoplasmic reticulum contact sites. We demonstrate here that individual plant subunits of ARP2/3 fused to fluorescent proteins form motile dot-like structures in the cytoplasm that are associated with plant peroxisomes. ARP2/3 dot structure is found at the peroxisome periphery and contains assembled ARP2/3 complex and WAVE/SCAR complex subunit NAP1. This dot occasionally colocalizes with the autophagosome, and under conditions that affect the autophagy, colocalization between ARP2/3 and the autophagosome increases. ARP2/3 subunits co-immunoprecipitate with ATG8f marker. Since mutants lacking functional ARP2/3 complex have more peroxisomes than WT, we link the ARP2/3 complex on peroxisomes to the process of peroxisome degradation by autophagy called pexophagy. Additionally, several other peroxisomal proteins colocalize with ARP2/3 dot on plant peroxisomes. Our results suggest a specific role of ARP2/3 and actin in the peroxisome periphery, presumably in membrane remodelling. We hypothesize that this role of ARP2/3 aids processes at the peroxisome periphery such as peroxisome degradation through autophagy or regulation of peroxisomal proteins localization or function. Significance statementARP2/3 complex-positive dots associate exclusively with peroxisomes in plant cells, where it colocalizes with autophagosome marker ATG8f and several other proteins. Our experiments link ARP2/3 to pexophagy: colocalization between ARP2/3 dots and autophagosome increases when autophagy processes are induced or inhibited; ARP2/3 and ATG8f colocalize and co-immunoprecipitate, and finally, ARP2/3 mutants cells contain more peroxisomes than WT. Our results suggest a novel role of ARP2/3 in peroxisome structure and function regulation.

cell biology↗