Biology subjects

Conrad, J. C.

Publications and source records attributed to Conrad, J. C..

3 recordsLinked to original sources

bioRxiv2022

In BRAFV600E-mutated colorectal cancer cells, fascin1 restructures adherens junctions to drive Wnt activation

Fascin1 expression in colorectal carcinomas (CRCs) is linked to a clinically aggressive disease with poor prognosis. Despite that fascin1s role in the etiology of CRCs has not been directly investigated. We show fascin1 expression in one-third of all CRCs underscoring the critical need to identify fascin1s function in colorectal carcinogenesis. Here, we identify for the first time, fascin1s role as a mechanosensor that modulates CRC cell adherens junction (AJ) plasticity to induce tumor growth and metastasis. We show that fascin1 expression drives protein sorting to transform AJ mechanotransduction and we reveal how these force-sensitive pathways activate oncogenic signaling in CRC cells. We made the novel finding that AJ remodeling by fascin1 also controls "collective plasticity" and bidirectional cell migration. Few studies have examined AJ plasticity in cancer cells, which remains poorly understood and has not been therapeutically targeted. Our findings could have widespread implications for understanding and treating metastatic carcinomas.

cancer biology↗

bioRxiv2022

Systematic Design of Pulse Dosing to Eradicate Persister Bacteria

A small fraction of infectious bacteria use persistence as a strategy to survive exposure to antibiotics. Periodic pulse dosing of antibiotics has long been considered a potentially effective strategy towards eradication of persisters. Recent studies have demonstrated through in vitro experiments that it is indeed feasible to achieve such effectiveness. However, systematic design of periodic pulse dosing regimens to treat persisters is currently lacking. Here we rigorously develop a methodology for the systematic design of optimal periodic pulse dosing strategies for rapid eradication of persisters. A key outcome of the theoretical analysis, on which the proposed methodology is based, is that bactericidal effectiveness of periodic pulse dosing depends mainly on the ratio of durations of the corresponding on and off parts of the pulse. Simple formulas for critical and optimal values of this ratio are derived. The proposed methodology is supported by computer simulations and in vitro experiments. Author SummaryAdministering antibiotics in periodic pulses that alternate between high and low concentration has long been known as a possible dosing strategy to treat stubborn infections caused by bacteria known as persisters. Such bacteria use clever mechanisms to survive otherwise lethal temporary exposure to antibiotics and to resume normal activity upon antibiotic removal. Persisters pose a serious health problem. Recent studies have elucidated mechanisms of persistence and have confirmed that pulse dosing, if designed appropriately, can indeed be effective. However, effective pulse dosing design has been mainly handled by trial and error, requiring relatively extensive experimentation. Here we develop a method for rapid systematic design of effective pulse dosing. The method relies on a simple mathematical model and a minimal amount of standard experimental data. We derive corresponding design formulas that explicitly characterize the shape of generally effective or optimal periodic pulses. We tested our method through computer simulations and in vitro experiments, as well as on prior literature data. In all cases, the outcomes on persister bacteria eradication predicted by our method were confirmed. These results pave the way for ultimately developing effective pulse dosing regimens in realistic situations in vivo.

systems biology↗

bioRxiv2018

Weakly-bound Dimers that Underlie the Crystal Nucleation Precursors in Lysozyme Solutions

Protein crystallization is central to understanding of molecular structure in biology, a vital part of processes in the pharmaceutical industry, and a crucial component of numerous disease pathologies. Crystallization starts with nucleation and how nucleation proceeds determines the crystallization rate and essential properties of the resulting crystal population. Recent results with several proteins indicate that crystals nucleate within preformed mesoscopic protein-rich clusters. The origin of the mesoscopic clusters is poorly understood. In the case of lysozyme, a common model of protein biophysics, earlier findings suggest that clusters exist owing to the dynamics of formation and decay of weakly-bound transient dimers. Here we present evidence of a weakly bound lysozyme dimer in solutions of this protein. We employ two electrospray mass spectrometry techniques, a combined ion mobility separation mass spectrometry and a high-resolution implementation. To enhance the weak but statistically-significant dimer signal we develop a method based on the residuals between the maxima of the isotope peaks in Fourier space and their Gaussian envelope. We demonstrate that these procedures sensitively detect the presence of a non-covalently bound dimer and distinguish its signal from other polypeptides, noise, and sampling artefacts. These findings contribute essential elements of the crystal nucleation mechanism of lysozyme and other proteins and suggest pathways to control nucleation and crystallization by enhancing or suppressing weak oligomerization.

biophysics↗