LC3/GABARAP binding to fluid membranes is potentiated by ceramide

Varela, Yaiza R.; Alonso, Alicia

doi:10.1080/15548627.2022.2136821

Cited by 4 publications

(8 citation statements)

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“…In previous work [ 11 , 12 ], two different mechanisms by which ceramide increases LC3/GABARAP binding to CL-containing bilayers were proposed: either Cer present in the liquid phase was mainly responsible or the presence of ceramide in the membrane produced a lipid restructuring, which favors the protein binding. In order to elucidate this mechanism, differential scanning calorimetry (DSC), confocal microscopy, and atomic force microscopy (AFM) were performed.…”

Section: Discussionmentioning

confidence: 99%

“…In our recent article [ 11 , 12 ], how the binding of LC3/GABARAP autophagy proteins to eSM:DOPE bilayers containing CL was enhanced by the presence of Cer was shown. Fluorescence microscopy of GUV revealed that in eSM:DOPE:CL:Cer mixtures, Cer gave rise to laterally segregated and highly rigid domains, in agreement with previous observations [ 18 , 35 , 36 , 37 , 38 ].…”

Section: Discussionmentioning

confidence: 99%

“…Further studies from our group include the role of cardiolipin (CL)-LC3/GABARAP interactions in mitophagy [ 9 , 10 ] and more recently, the capacity of ceramide (Cer) to enhance the binding of LC3/GABARAP autophagy proteins to CL-containing membranes in mitophagy, the specific degradation of mitochondria via autophagy [ 11 , 12 ]. A substantial part of these investigations has been carried out on model membranes of defined lipid compositions.…”

Section: Introductionmentioning

confidence: 99%

“…The present contribution arises from our recent studies described in [ 11 , 12 ]. Those investigations were based on bilayers composed of egg sphingomyelin (eSM), dioleoyl phosphatidyl ethanolamine (DOPE), and CL.…”

Section: Introductionmentioning

confidence: 99%

“…Ceramide in turn is a non-phosphoryl-containing sphingolipid, characterized by an extremely low polarity [ 18 ]. The data by Varela et al [ 11 , 12 ] showed that, when incorporated into a matrix of egg SM and DOPE, CL was essential for LC3/GABARAP interaction with these bilayers and that Cer markedly increased binding. Moreover, giant unilamellar vesicles (GUV) examined under confocal fluorescence microscopy revealed that Cer segregated laterally into very rigid domains, while GABARAP bound only the more fluid regions, suggesting that the enhancing role of ceramide is exerted by the minority of ceramide molecules dispersed in the fluid phase.…”

Section: Introductionmentioning

confidence: 99%

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Lipids in Mitochondrial Macroautophagy: Phase Behavior of Bilayers Containing Cardiolipin and Ceramide

Varela

González-Ramírez

Etxaniz

et al. 2023

IJMS

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Cardiolipin (CL) is a key lipid for damaged mitochondrial recognition by the LC3/GABARAP human autophagy proteins. The role of ceramide (Cer) in this process is unclear, but CL and Cer have been proposed to coexist in mitochondria under certain conditions. Varela et al. showed that in model membranes composed of egg sphingomyelin (eSM), dioleoyl phosphatidylethanolamine (DOPE), and CL, the addition of Cer enhanced the binding of LC3/GABARAP proteins to bilayers. Cer gave rise to lateral phase separation of Cer-rich rigid domains but protein binding took place mainly in the fluid continuous phase. In the present study, a biophysical analysis of bilayers composed of eSM, DOPE, CL, and/or Cer was attempted to understand the relevance of this lipid coexistence. Bilayers were studied by differential scanning calorimetry, confocal fluorescence microscopy, and atomic force microscopy. Upon the addition of CL and Cer, one continuous phase and two segregated ones were formed. In bilayers with egg phosphatidylcholine instead of eSM, in which the binding of LC3/GABARAP proteins hardly increased with Cer in the former study, a single segregated phase was formed. Assuming that phase separation at the nanoscale is ruled by the same principles acting at the micrometer scale, it is proposed that Cer-enriched rigid nanodomains, stabilized by eSM:Cer interactions formed within the DOPE- and CL-enriched fluid phase, result in structural defects at the rigid/fluid nanointerfaces, thus hypothetically facilitatingLC3/GABARAP protein interaction.

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Section: Discussionmentioning

confidence: 99%