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Mammalian phospholipid homeostasis: evidence that membrane curvature elastic stress drives homeoviscous adaptation in vivo.

ABSTRACT: Several theories of phospholipid homeostasis have postulated that cells regulate the molecular composition of their bilayer membranes, such that a common biophysical membrane parameter is under homeostatic control. Two commonly cited theories are the intrinsic curvature hypothesis, which states that cells control membrane curvature elastic stress, and the theory of homeoviscous adaptation, which postulates cells control acyl chain packing order (membrane order). In this paper, we present evidence from data-driven modelling studies that these two theories correlate in vivo. We estimate the curvature elastic stress of mammalian cells to be 4-7 × 10(-12) N, a value high enough to suggest that in mammalian cells the preservation of membrane order arises through a mechanism where membrane curvature elastic stress is controlled. These results emerge from analysing the molecular contribution of individual phospholipids to both membrane order and curvature elastic stress in nearly 500 cellular compositionally diverse lipidomes. Our model suggests that the de novo synthesis of lipids is the dominant mechanism by which cells control curvature elastic stress and hence membrane order in vivo These results also suggest that cells can increase membrane curvature elastic stress disproportionately to membrane order by incorporating polyunsaturated fatty acids into lipids.

SUBMITTER: Dymond MK

PROVIDER: S-EPMC5014058 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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Mammalian phospholipid homeostasis: evidence that membrane curvature elastic stress drives homeoviscous adaptation in vivo.

Dymond Marcus K MK

Journal of the Royal Society, Interface 20160801 121

Several theories of phospholipid homeostasis have postulated that cells regulate the molecular composition of their bilayer membranes, such that a common biophysical membrane parameter is under homeostatic control. Two commonly cited theories are the intrinsic curvature hypothesis, which states that cells control membrane curvature elastic stress, and the theory of homeoviscous adaptation, which postulates cells control acyl chain packing order (membrane order). In this paper, we present evidenc ...[more]

PMID: 27534697

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Project description:UNLABELLED:Phage shock protein A (PspA), which is responsible for maintaining inner membrane integrity under stress in enterobacteria, and vesicle-inducting protein in plastids 1 (Vipp1), which functions for membrane maintenance and thylakoid biogenesis in cyanobacteria and plants, are similar peripheral membrane-binding proteins. Their homologous N-terminal amphipathic helices are required for membrane binding; however, the membrane features recognized and required for expressing their functionalities have remained largely uncharacterized. Rigorously controlled, in vitro methodologies with lipid vesicles and purified proteins were used in this study and provided the first biochemical and biophysical characterizations of membrane binding by PspA and Vipp1. Both proteins are found to sense stored curvature elastic (SCE) stress and anionic lipids within the membrane. PspA has an enhanced sensitivity for SCE stress and a higher affinity for the membrane than Vipp1. These variations in binding may be crucial for some of the proteins' differing roles in vivo. Assays probing the transcriptional regulatory function of PspA in the presence of vesicles showed that a relief of transcription inhibition occurs in an SCE stress-specific manner. This in vitro recapitulation of membrane stress-dependent transcription control suggests that the Psp response may be mounted in vivo when a cell's inner membrane experiences increased SCE stress. IMPORTANCE:All cell types maintain the integrity of their membrane systems. One widely distributed membrane stress response system in bacteria is the phage shock protein (Psp) system. The central component, peripheral membrane protein PspA, which mitigates inner membrane stress in bacteria, has a counterpart, Vipp1, which functions for membrane maintenance and thylakoid biogenesis in plants and photosynthetic bacteria. Membrane association of both these proteins is accepted as playing a pivotal role in their functions. Here we show that direct membrane binding by PspA and Vipp1 is driven by two physio-chemical signals, one of which is membrane stress specific. Our work points to alleviation of membrane stored curvature elastic stress by amphipathic helix insertions as an attractive mechanism for membrane maintenance by PspA and Vipp1. Furthermore, the identification of a physical, stress-related membrane signal suggests a unilateral mechanism that promotes both binding of PspA and induction of the Psp response.

Dataset Information

Mammalian phospholipid homeostasis: evidence that membrane curvature elastic stress drives homeoviscous adaptation in vivo.

Publications

Mammalian phospholipid homeostasis: evidence that membrane curvature elastic stress drives homeoviscous adaptation in vivo.

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