Akt Is S-Palmitoylated: A New Layer of Regulation for Akt

Abstract

The protein kinase Akt/PKB participates in a great variety of processes, including translation, cell proliferation and survival, as well as malignant transformation and viral infection. In the last few years, novel Akt posttranslational modifications have been found. However, how these modification patterns affect Akt subcellular localization, target specificity and, in general, function is not thoroughly understood. Here, we postulate and experimentally demonstrate by acyl-biotin exchange (ABE) assay and 3H-palmitate metabolic labeling that Akt is S-palmitoylated, a modification related to protein sorting throughout subcellular membranes. Mutating cysteine 344 into serine blocked Akt S-palmitoylation and diminished its phosphorylation at two key sites, T308 and T450. Particularly, we show that palmitoylation-deficient Akt increases its recruitment to cytoplasmic structures that colocalize with lysosomes, a process stimulated during autophagy. Finally, we found that cysteine 344 in Akt1 is important for proper its function, since Akt1-C344S was unable to support adipocyte cell differentiation in vitro. These results add an unexpected new layer to the already complex Akt molecular code, improving our understanding of cell decision-making mechanisms such as cell survival, differentiation and death.

A Highly Sensitive Fluorescent Akt Biosensor Reveals Lysosome-Selective Regulation of Lipid Second Messengers and Kinase Activity

“…As seen in Figure e, Golgi-ExRai-AktAR2 colocalized with appropriate Golgi marker (Golgin-97) and responded to PDGF with a 169 ± 21% (Δ R / R 0 , n = 12) increase in the excitation ratio. In support of this notion, a recent study suggested that Akt and phosphoinositide-dependent kinase-1 (PDK1) are present in Golgi membranes, and Akt is regulated by S-palmitoylation, a protein lipidation that is reversible and often occurs in Golgi membranes . The specific regulation and functional role of this pool of Akt activity await further investigation.…”

Reduced S-acylation of SQSTM1/p62 in Huntington disease is associated with impaired autophagy

“…Palmitoylation likely regulates autophagy by acting as a mechanism for autophagy regulators to quickly localize to and from membranes during induction of autophagy. Recently, other regulators of autophagy have been shown to be palmitoylated, including, AKT, MTOR and LAMTOR1 17,30 . We predict that negative regulators of autophagy found at membrane interfaces, like MTOR, are palmitoylated when active and depalmitoylated when autophagy is activated.…”

How palmitoylation affects trafficking and signaling of membrane receptors

“…Indeed, agonist (isoproterenol) stimulation increases palmitoylation of both β 2 -AR (Mouillac et al, 1992) and its associated Gα proteins (Mumby et al, 1994). Another example is Akt which acts downstream of EGFR (Runkle et al, 2016) and many other signalling receptors, and that was recently found to be palmitoylated (Blaustein et al, 2021).…”