Membrane Disruption by Very Long Chain Fatty Acids during Necroptosis

Abstract

Necroptosis is a form of regulated cell death which results in loss of plasma membrane integrity, release of intracellular contents, and an associated inflammatory response. We previously found that saturated very long chain fatty acids (VLCFAs), which contain ≥20 carbons, accumulate during necroptosis. Here, we show that genetic knockdown of Fatty Acid (FA) Elongase 7 (ELOVL7) reduces accumulation of specific very long chain FAs during necroptosis, resulting in reduced necroptotic cell death and membrane permeabilization. Conversely, increasing the expression of ELOVL7 increases very long chain fatty acids and membrane permeabilization. In vitro, introduction of the VLCFA C24 FA disrupts bilayer integrity in liposomes to a greater extent than a conventional C16 FA. To investigate the microscopic origin of these observations, atomistic Molecular Dynamics (MD) simulations were performed. MD simulations suggest that fatty acids cause clear differences in bilayers based on length and that it is the interdigitation of C24 FA between the individual leaflets that results in disorder in the region and, consequently, membrane disruption. We synthesized clickable VLCFA analogs and observed that many proteins were acylated by VLCFAs during necroptosis. Taken together, these results confirm the active role of VLCFAs during necroptosis and point to multiple potential mechanisms of membrane disruption including direct permeabilization via bilayer disruption and permeabilization by targeting of proteins to cellular membranes by fatty acylation.

Deciphering the modifiers for phenotypic variability of X-linked adrenoleukodystrophy

“…The exact role of VLCFA in the pathogenesis of X-ALD remains unclear, and no correlation has been established between the concentration of VLCFA and the different phenotypes of X-ALD. The abnormally accumulated VLCFA can disrupt the integrity of the plasma membranes through interdigitating between the leaflets of the lipid bilayer and can induce lipotoxicity, endoplasmic reticulum stress, mitochondrial dysfunction, and oxidative stress leading to apoptosis favoring the process of cerebral demyelination in the brain[ 5 - 8 ].…”

Human Cytomegalovirus uses a Host Stress Response to Balance the Elongation of Saturated/Monounsaturated and Polyunsaturated Very Long Chain Fatty Acids

“…This idea is further supported by the observation that the virus envelope of HCMV is enriched with PLs, with SFA/MUFA VLCFA tails (13, 38). While HCMV replication depends on ELOVL7 activity, the overproduction of saturated VLCFAs by ELOVL7 is cytotoxic (39) and PC, DG, and TG lipids with SFA/MUFA VLCFA tails increase during necroptosis (40). An increase in lipotoxicity could reduce viral replication if cell death occurs before the production of viral progeny.…”

Peroxisomes form intralumenal vesicles with roles in fatty acid catabolism and protein compartmentalization in Arabidopsis

“…The tendency of long-chain fatty acids to partition into lipid bilayers may lessen accessibility to the carnitine shuttle used by mitochondria to import fatty acids across the two lipid bilayers to the catabolic enzymes in the matrix. Moreover, free fatty acids can permeabilize lipid bilayers, particularly if the fatty acid is long enough to interact with the acyl chains of the opposite leaflet 56 . Because oxidative phosphorylation requires high membrane integrity, mitochondria may be particularly sensitive to these membrane-permeabilizing effects.…”