Henggeler, A. | bioRxiv Science

bioRxiv2024

FilamentID reveals the composition and function of metabolic enzyme polymers during gametogenesis

Gamete formation and subsequent offspring development often involve extended phases of suspended cellular development or even dormancy. How cells adapt to recover and resume growth remains poorly understood. Here, we visualized budding yeast cells undergoing meiosis by cryo-electron tomography (cryoET) and discovered elaborate filamentous assemblies decorating the nucleus, cytoplasm, and mitochondria. To determine filament composition, we developed a "Filament IDentification" (FilamentID) workflow that combines multiscale cryoET/cryo-electron microscopy (cryoEM) analyses of gently lysed cells. FilamentID identified the mitochondrial filaments as the conserved aldehyde dehydrogenase Ald4ALDH2 and the nucleoplasmic/cytoplasmic filaments being composed of acetyl-CoA synthetase Acs1ACSS2. The near-native high-resolution structures revealed the mechanism underlying polymerization and enabled us to perturb filament formation. Acs1 polymerization facilitates the recovery of chronologically aged spores, and more generally, the cell cycle re-entry of starved cells. FilamentID is broadly applicable to characterize filaments of unknown identity in diverse cellular contexts. HIGHLIGHTSO_LIFilamentID: a multiscale imaging workflow to characterize cellular filaments of unknown composition C_LIO_LIThe conserved aldehyde dehydrogenase Ald4ALDH2 polymerizes into filament arrays within meiotic mitochondria C_LIO_LIThe conserved acetyl-CoA synthetase Acs1ACSS2 forms filament arrays in the nucleus and the cytoplasm C_LIO_LIMetabolites mediate Acs1 polymerization to store Acs1 in an inactive state in gametes and starved cells C_LIO_LIAcs1 filament formation is required for efficient return to growth from starvation stress C_LI

cell biology↗

bioRxiv2019

The CHORD protein CHP-1 regulates EGF receptor trafficking and signaling in C. elegans and human cells

The intracellular trafficking of growth factor receptors determines the activity of their downstream signaling pathways. The putative co-chaperone CHP-1 acts as a regulator of EGFR trafficking during C.elegans vulval development. Loss of chp-1 causes the retention of the EGFR in the ER and decreased MAPK signaling. CHP-1 functions specifically, as the localization of other receptors is unaltered in chp-1(lf) mutants, and inhibiting other co-chaperones does not affect EGFR localization. The role of CHP-1 during EGFR trafficking is conserved in humans. Analogous to C.elegans, the response of CHP-1-deficient human cells to EGF stimulation is attenuated, the EGFR accumulates in the ER and ERK2 activity is decreased. Although CHP-1 has been proposed to act as a co-chaperone for HSP90, our data indicate an HSP90-independent function of CHP-1. The identification of CHP-1 as a regulator of EGFR trafficking opens the possibility to identify small molecule chaperone inhibitors targeting the EGFR pathway with increased selectivity.

cell biology↗