Response to Biophysical Journal comment to the editor by Skóra regarding the article entitled: Vast heterogeneity in cytoplasmic diffusion rates revealed by nanorheology and Doppelgänger simulations.

In a Comment to the Editor, Skóra raises a concern that the modeling framework implemented in Garner et al. (Biophysical Journal, 2023) neglects a potentially important term in the Brownian dynamics simulation of diffusion. Omission of this diffusivity gradient term may lead to an underestimation of the mean and overestimation of the variance of the cytoplasmic viscosity.

A conserved pressure-driven mechanism for regulating cytosolic osmolarity.

Controlling intracellular osmolarity is essential to all cellular life. Cells that live in hypo-osmotic environments, such as freshwater, must constantly battle water influx to avoid swelling until they burst. Many eukaryotic cells use contractile vacuoles to collect excess water from the cytosol and pump it out of the cell.

A conserved pressure-driven mechanism for regulating cytosolic osmolarity.

Controlling intracellular osmolarity is essential to all cellular life. Cells that live in hypo-osmotic environments like freshwater must constantly battle water influx to avoid swelling until they burst. Many eukaryotic cells use contractile vacuoles to collect excess water from the cytosol and pump it out of the cell.

Vast heterogeneity in cytoplasmic diffusion rates revealed by nanorheology and Doppelgänger simulations.

The cytoplasm is a complex, crowded, actively driven environment whose biophysical characteristics modulate critical cellular processes such as cytoskeletal dynamics, phase separation, and stem cell fate. Little is known about the variance in these cytoplasmic properties. Here, we employed particle-tracking nanorheology on genetically encoded multimeric 40 nm nanoparticles (GEMs) to measure diffusion within the cytoplasm of individual fission yeast (Schizosaccharomyces pombe) cellscells.

Leading edge maintenance in migrating cells is an emergent property of branched actin network growth.

Animal cell migration is predominantly driven by the coordinated, yet stochastic, polymerization of thousands of nanometer-scale actin filaments across micron-scale cell leading edges. It remains unclear how such inherently noisy processes generate robust cellular behavior. We employed high-speed imaging of migrating neutrophil-like HL-60 cells to explore the fine-scale shape fluctuations that emerge and relax throughout the process of leading edge maintenance.

Neutrophil-like HL-60 cells expressing only GFP-tagged β-actin exhibit nearly normal motility.

Observations of actin dynamics in living cells using fluorescence microscopy have been foundational in the exploration of the mechanisms underlying cell migration. We used CRISPR/Cas9 gene editing to generate neutrophil-like HL-60 cell lines expressing GFP-β-actin from the endogenous locus (ACTB). In light of many previous reports outlining functional deficiencies of labeled actin, we anticipated that HL-60 cells would only tolerate a monoallelic edit, as biallelic edited cells would produce no normal β-actin.

Erratum for Foe et al., "The Toxoplasma gondii Active Serine Hydrolase 4 Regulates Parasite Division and Intravacuolar Parasite Architecture".

[This corrects the article DOI: 10.1128/mSphere.00393-18.

The Active Serine Hydrolase 4 Regulates Parasite Division and Intravacuolar Parasite Architecture.

Hydrolase are enzymes that regulate diverse biological processes, including posttranslational protein modifications. Recent work identified four active serine hydrolases (ASHs) in as candidate depalmitoylases. However, only () has been confirmed to remove palmitate from proteins.