Miscibility Transition Temperature Scales with Growth Temperature in a Zebrafish Cell Line

Abstract

Cells can alter the lipid content of their plasma membranes upon changes in their environment to maintain and adjust membrane function. Recent work suggests that some membrane functions arise because cellular plasma membranes are poised close to a miscibility transition under growth conditions. Here we report experiments utilizing giant plasma membrane vesicles (GPMVs) to explore how membrane transition temperature varies with growth temperature in a zebrafish cell line (ZF4) that can be adapted for growth between 20 and 32°C. We find that GPMV transition temperatures adjust to be 16.7 ± 1.2°C below growth temperature for four growth temperatures investigated and that adjustment occurs over roughly 2 days when temperature is abruptly lowered from 28 to 20°C. We also find that GPMVs have slightly different lipidomes when isolated from cells adapted for growth at 28 and 20°C. Similar to past work in vesicles derived from mammalian cells, fluctuating domains are observed in ZF4-derived GPMVs, consistent with their having critical membrane compositions. Taken together, these experimental results suggest that cells in culture biologically tune their membrane composition in a way that maintains specific proximity to a critical miscibility transition.

Regulating lipid composition rationalizes acyl-tail saturation homeostasis in ectotherms

“…This provides a rationale for lipid changes observed in (19): under the homeoviscous hypothesis, cholesterol concentration must increase with temperature in order to compensate for the decrease in viscosity induced by temperature. Furthermore, acyl tail saturation changes are surprisingly similar to those of (19). This also provides an explanation for the correlation between cholesterol enrichment (9) and acyl tail desaturation (10).…”

Low membrane fluidity triggers lipid phase separation and protein segregation in vivo

“…Finally, our results provide direct in vivo support for current in vitro and in silico models regarding lipid phase separation and associated protein segregation.Keywords: Lipid phase separation, lipid domains, protein partitioning, membrane fluidity, homeoviscous adaptation, Escherichia coli, Bacillus subtilis, WALP, FOF1 ATP synthase liquid-disordered phase characterized by low packing density and high diffusion rates that forms the regular state of biological membranes, (ii) the more ordered, cholesterol/hopanoid-dependent liquidordered phase found in biological membranes in form of lipid rafts, and (iii) the gel phase characterized by dense lipid packing with little lateral or rotational diffusion, which is generally assumed to be absent in biologically active membranes (Schmid, 2017;Veatch, 2007). In fact, the temperature associated with gel phase formation has been postulated to define the lower end of the temperature range able to support vital cell functions (Burns et al, 2017;Drobnis et al, 1993;Ghetler et al, 2005). At last, the lipid phases can co-exist, resulting in separated membrane areas exhibiting distinctly different composition and characteristics (Baumgart et al, 2007;Elson et al, 2010;Heberle and Feigenson, 2011).…”

Using spectral decomposition of the signals from laurdan-derived probes to evaluate the physical state of membranes in live cells

“…Are the authors sure that this is what happens? Can that be something else?3min pictures in Fig7 is different than the rest, why?For Figure 10-13, it is necessary to show some quantification, qualitative assessment with the colors isn’t enough.“Considering the importance of temperature in regulating the state and order in lipid bilayers….” Authors should give a reference here such as Burns et al , 2017 7 .In the first paragraph of the Discussion, authors should also discuss the recently published improved approach of spectral imaging analysis (Aron et al , 2017 8 )In the discussion, when authors discuss the differences of lipid packing, they only consider the lipid composition. They should also add a short discussion on the presence of actin cytoskeleton for plasma membrane (and absence of it for intracellular membranes) may be responsible for relatively more ordered plasma membrane compared to intracellular ones (Dinic et al , 2013 9 ).…”

“…“Considering the importance of temperature in regulating the state and order in lipid bilayers….” Authors should give a reference here such as Burns et al , 2017 7 .…”