Biology subjects

Davies, K. A.

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

3 recordsLinked to original sources

bioRxiv2024

Unconventional binding of Calmodulin to CHK2 kinase inhibits catalytic activity

Calmodulin (CaM) serves an essential role in eukaryotic cells as a Ca2+ sensor. Ca2+ binding leads to conformation changes in CaM that enable engagement of a repertoire of enzymes and the regulation of their catalytic activities. Classically, Ca2+-CaM binds to an inhibitory pseudosubstrate sequence C-terminal to the kinase domain in members of the Ca2+-CaM dependent protein kinase (CAMK) family, and relieves inhibition to promote catalytic activity. Here, we report an unexpected mechanism by which CaM can bind CHK2 kinase to inhibit its kinase activity. Using biochemical, biophysical, structural mass spectrometry, and cellular approaches, we identify a direct interaction of Ca2+-CaM with the CHK2 kinase domain that suppresses CHK2 catalytic activity in vitro and is crucial for cell proliferation in human cells following DNA damage. Our findings add direct suppression of kinase activity to the repertoire of CaMs functions, complementing the paradigmatic mechanism of promoting kinase activity through autoinhibitory domain sequestration.

biochemistry↗

bioRxiv2021

Membrane permeabilization is mediated by distinct epitopes in mouse and human orthologs of the necroptosis effector, MLKL

Necroptosis is a lytic programmed cell death pathway with origins in innate immunity that is frequently dysregulated in inflammatory diseases. The terminal effector of the pathway, MLKL, is licensed to kill following phosphorylation of its pseudokinase domain by the upstream regulator, RIPK3 kinase. Phosphorylation provokes the unleashing of MLKLs N-terminal four-helix bundle (4HB or HeLo) domain, which binds and permeabilizes the plasma membrane to cause cell death. The precise mechanism by which the 4HB domain permeabilizes membranes, and how the mechanism differs between species, remains unclear. Here, we identify the membrane binding epitope of mouse MLKL using NMR spectroscopy. Using liposome permeabilization and cell death assays, we validate K69 in the 3 helix, W108 in the 4 helix, and R137/Q138 in the first brace helix as crucial residues for necroptotic signaling. This epitope differs from the phospholipid binding site reported for human MLKL, which comprises basic residues primarily located in the 1 and 2 helices. In further contrast to human and plant MLKL orthologs, in which the 3-4 loop forms a helix, this loop is unstructured in mouse MLKL in solution. Together, these findings illustrate the versatility of the 4HB domain fold, whose lytic function can be mediated by distinct epitopes in different orthologs.

cell biology↗

bioRxiv2018

SOL1 and SOL2 Regulate Fate Transition and Cell Divisions in the Arabidopsis Stomatal Lineage

In the stomatal lineage, cells make fate transitions from asymmetrically dividing and self-renewing meristemoids, to commitment to the guard mother cell identity, and finally though a single division to create mature, post-mitotic stomatal guard cells. Flexibility in the stomatal lineage allows plants to alter leaf size and stomatal density in response to environmental conditions; however, transitions must be clean and unidirectional in order to produce functional and correctly patterned stomata. Among direct transcriptional targets of the stomatal initiating factor, SPEECHLESS, we found a pair of genes, SOL1 and SOL2, required for effective transitions in the lineage. Here we show that these two genes, which are homologues of the LIN54 DNA-binding components of the mammalian DREAM complex, are expressed in a cell cycle dependent manner and regulate cell fate and division properties in the self-renewing early lineage. In the terminal division of the stomatal lineage, however, these two proteins appear to act in opposition to their closest paralogue, TSO1, revealing complexity in the gene family may enable customization of cell divisions in coordination with development.

developmental biology↗