Biology subjects

Kowallis, K. A.

Publications and source records attributed to Kowallis, K. A..

3 recordsLinked to original sources

bioRxiv2020

Scaffold-scaffold interactions regulate cell polarity in a bacterium

The localization of two biochemically distinct signaling hubs at opposite cell poles provides the foundation for asymmetric cell division in Caulobacter crescentus. Here we identify an interaction between the scaffolds PodJ and PopZ that regulates the assembly of the new cell pole signaling complex. Time-course imaging of a mCherry-sfGFP-PopZ fluorescent timer throughout the cell cycle revealed that existing PopZ resides at the old cell pole while newly translated PopZ accumulates at the new cell pole. Our studies suggest that interactions between PodJ and PopZ promotes the sequestration of older PopZ and robust accumulation of newl PopZ at the new cell pole. Elimination of the PodJ-PopZ interaction impacts PopZ client proteins, leading to chromosome segregation defects in one-third of cells. Additionally, this PopZ-PodJ interaction is crucial for anchoring PodJ and preventing PodJ extracellular loss at the old cell pole through unknown mechanism. Therefore, segregation of PopZ protein at the old pole and recruitment of newly translated PopZ at the new pole via the PodJ scaffold ensures stringent inheritance and maintenance of the polarity axis within dividing C. crescentus cells.

microbiology↗

bioRxiv2019

Reversed Signaling Flow of a Bacterial Pseudokinase

Bacteria respond to environmental and cellular cues both through isolated signaling events between one sensor histidine kinase and its response regulator, and through more interconnected arrays. Caulobacter crescentus achieves asymmetric division through a network of histidine kinases, and here we interrogate a novel DivL pseudokinase reverse signaling mechanism that enables productive cross-talk across the network. A leucine zipper fusion method was used to synthetically stimulate reverse signaling between the sensor and kinase domains and directly test if reverse signaling could modulate the signaling network in vivo. Stimulation of sensor-kinase helix conformational changes resulted in changes in C. crescentus motility and DivL accumulation at the cell poles. The repurposed roles of the sensor domain in these processes were evaluated. We demonstrate that a domain of unknown function that binds to two scaffolding proteins, and two conserved signaling domains are employed as modulators of an active kinase. We propose that reversed signaling may be widely used across signaling enzymes.

microbiology↗

bioRxiv2018

A circuit of protein-protein regulatory interactions enables polarity establishment in a bacterium

Asymmetric cell division generates specialized daughter cells that play a variety of roles including tissue morphogenesis in eukaryotes and pathogenesis in bacteria. In the gram-negative bacterium Caulobacter crescentus, asymmetric localization of two biochemically distinct signaling hubs at opposite cell poles provides the foundation for asymmetric cell division. Through a set of genetic, synthetic biology and biochemical approaches we have characterized the regulatory interactions between three scaffolding proteins. These studies have revealed that the scaffold protein PodJ functions as a central mediator for organizing the new cell signaling hub, including promoting bipolarization of the central developmental scaffold protein PopZ. In addition, we identified that the old pole scaffold SpmX serves as a negative regulator of PodJ subcellular accumulation. These two scaffold-scaffold regulatory interactions serve as the core of an integrated cell polarization circuit that is layered on top of the cell-cycle circuitry to coordinate cell differentiation and asymmetric cell division.

microbiology↗