Morgan, F. | Search bioRxiv

bioRxiv2019

Criticality of plasma membrane lipids reflects activation state of macrophage cells

Signalling is of particular importance in immune cells, and upstream in the signalling pathway many membrane receptors are functional only as complexes, co-locating with particular lipid species. Work over the last 15 years has shown that plasma membrane lipid composition is close to a critical point of phase separation, with evidence that cells adapt their composition in ways that alter the proximity to this thermodynamical point. Macrophage cells are a key component of the innate immune system, responsive to infections, regulating the local state of inflammation. We investigate changes in the plasma membranes proximity to the critical point, as a response to stimulation by various pro- and anti-inflammatory agents. Pro-inflammatory (IFN-{gamma}, Kdo-LipidA, LPS) perturbations induce an increase in the transition temperature of the GMPVs; anti-inflammatory IL4 has the opposite effect. These changes recapitulate complex plasma membrane composition changes, and are consistent with lipid criticality playing a master regulatory role: being closer to critical conditions increases membrane protein activity.

biophysics↗

bioRxiv2019

Antarctica's wilderness has declined to the exclusion of biodiversity

Recent assessments of the biodiversity value of Earth's dwindling wilderness areas have emphasized the whole of Antarctica as a crucial wilderness in need of urgent protection. Whole-of-continent designations for Antarctic conservation remain controversial, however, because of widespread human impacts and frequently used provisions in Antarctic law for the designation of specially protected areas to conserve wilderness values, species and ecosystems. Here we investigate the extent to which Antarctica's wilderness encompasses its biodiversity. We assembled a comprehensive record of human activity on the continent (~ 2.7 million localities) and used it to identify unvisited areas [≥] 10 000 km2 (i.e. Antarctica's wilderness areas) and their representation of biodiversity. We show that, at best, 7 770 000 km2 of wilderness remains, covering 56.9% of the continent's surface area, however it captures few important biodiversity features. Important Bird Areas, ice-free Antarctic Conservation Biogeographic Regions crucial for biodiversity and areas with verified biodiversity records are largely excluded. Our results demonstrate that Antarcticas wilderness has already declined to the exclusion of much of its biodiversity. But that on a continent set aside as a natural reserve, increased regulation of human activity and urgent expansion of the Antarctic specially protected area network could feasibly reverse this trend.

ecology↗