S-Acylation and Cellular Handling of SARS-CoV-2 Spike Protein: A Falsifiable Hypothesis on Post-Expression Retention

This hypothesis article examines whether the established effects of S-acylation (palmitoylation) on full-length SARS-CoV-2 Spike biogenesis and hours-long protein turnover extend to experimentally detectable differences in post-expression cellular retention, clearance, or longer-lived compartmentalization. The manuscript does not claim that prolonged Spike retention has been demonstrated as a consequence of S-acylation, that Spike preferentially accumulates in adipose tissue, or that persistent Spike-derived antigen causes Long COVID, post-vaccination symptoms, coagulation abnormalities, or other clinical outcomes. The proposed mechanism is presented as a falsifiable experimental hypothesis rather than an established explanation for human disease. The hypothesis is grounded in experimentally established effects of Spike S-acylation on biogenesis, degradation, intracellular trafficking, membrane organization, fusion, and infectivity. Human observations of SARS-CoV-2 antigen or RNA persistence following infection and the more limited observations following vaccination are reviewed separately and are not treated as biologically interchangeable. Evidence concerning the clinical significance of post-infection viral or antigen persistence is treated as unresolved. Some tissue studies have reported associations between persistent SARS-CoV-2 RNA and Long COVID symptoms, whereas longitudinal antigen studies have found little or no association between detectable circulating antigen and persistent symptom burden. Detection of viral RNA, full-length Spike, S1, or other viral antigens is therefore not treated as evidence, by itself, of symptom causation. The manuscript distinguishes full-length Spike from S1 and other Spike-derived material, and distinguishes membrane lipid nanodomains from adipocyte neutral-lipid storage. Adipose tissue is treated as an experimentally testable compartment, not as an established preferential reservoir. Negative longer-term evidence regarding SARS-CoV-2 RNA in subcutaneous adipose tissue is included. The central experimental prediction is narrow: the already established S-acylation-dependent turnover phenotype should extend beyond the hours-long measurements reported previously if it materially promotes prolonged cellular retention. After synchronized cessation of Spike expression, palmitoylation-competent and -deficient Spike should therefore show reproducible differences in prespecified retention or clearance outcomes. Conversely, if the known short-timescale turnover difference is reproduced but longer-term post-expression retention is unchanged, the proposed extension should be rejected or substantially revised.