S-acylation in apoptotic and non-apoptotic cell death: a central regulator of membrane dynamics and protein function

Abstract

Protein lipidation is a collection of important post-translational modifications that modulate protein localization and stability. Protein lipidation affects protein function by facilitating interactions with cellular membranes, changing the local environment of protein interactions. Among these modifications, S-acylation has emerged as a key regulator of various cellular processes, including different forms of cell death. In this mini-review, we highlight the role of S-acylation in apoptosis and its emerging contributions to necroptosis and pyroptosis. While traditionally associated with the incorporation of palmitic acid (palmitoylation), recent findings indicate that other fatty acids can also participate in S-acylation, expanding its functional repertoire. In apoptosis, S-acylation influences the localization and function of key regulators such as Bcl-2-associated X protein and other proteins modulating their role in mitochondrial permeabilization and death receptor signaling. Similarly, in necroptosis, S-acylation of mixed lineage kinase domain-like protein (MLKL) with palmitic acid and very long-chain fatty acids enhances membrane binding and membrane permeabilization, contributing to cell death and inflammatory responses. Recent studies also highlight the role of S-acylation in pyroptosis, where S-acylated gasdermin D facilitates membrane localization and pore assembly upon inflammasome activation. Blocking palmitoylation has shown to suppress pyroptosis and cytokine release, reducing inflammatory activity and tissue damage in septic models. Collectively, these findings underscore S-acylation as a shared and important regulatory mechanism across cell death pathways affecting membrane association of key signaling proteins and membrane dynamics, and offer insights into the spatial and temporal control of protein function.

Keywords: S-acylation; apoptosis; cell death; necroptosis; palmitoylation; pyroptosis.

Figure 1. Major types of protein lipidation.

S-acylation promoted by protein acyltransferases results in the covalent addition of fatty acids, shown in blue, to cysteine residues. Farnesyl and geranylgeranyl transferases mediated isoprenylation, involving the transfer of isoprene units (farnesyl diphosphate and geranylgeranyl diphosphatase, respectively), shown in red, to thiol groups present in cysteine residues near the C-terminal of proteins. N-myristoyltransferase catalyzed the transfer of myristic acid to the N-terminal glycine of proteins. C-terminal glycine residues can be modified with cholesterol via ester linkages, resulting in cholesterylation.

Figure 2. S-acylation in apoptosis, necroptosis and pyroptosis.

(A) During the intrinsic apoptosis pathway, pro-apoptotic protein BAX is S-acylated at Cys126, facilitating its recruitment to the mitochondrial membrane. This recruitment enables BAX oligomerization, leading to mitochondrial membrane permeabilization. The permeabilized membrane allows cytochrome c release, caspase activation, and ultimately, apoptosis. Similarly, in the extrinsic pathway, the FAS receptor is S-acylated at Cys199, enhancing its membrane binding. This modification contributes to the activation of downstream caspases and triggers apoptosis. (B) In necroptosis, the formation of the phosphorylated RIPK1/RIPK3 necrosome initiates the recruitment and phosphorylation of MLKL. Phosphorylated MLKL undergoes selective S-acylation, which drives its translocation to the plasma membrane. At the membrane, this modification facilitates permeabilization and destabilization, leading to the loss of membrane integrity. This disruption contributes to the release of pro-inflammatory cytokines, a hallmark of necroptosis. (C) During pyroptosis, gasdermin D is cleaved by caspases, yielding its active form. The cleaved gasdermin D undergoes S-acylation, which enhances its ability to oligomerize and form pores in the plasma membrane. These pores exacerbate membrane disruption, driving pyroptosis.