The Assembly-Activating Protein Promotes Stability and Interactions between AAV’s Viral Proteins to Nucleate Capsid Assembly

• Published in: Cell reports (Cambridge) Vol. 23; no. 6; pp. 1817 - 1830
• Main Authors: Maurer, Anna C., Pacouret, Simon, Cepeda Diaz, Ana Karla, Blake, Jessica, Andres-Mateos, Eva, Vandenberghe, Luk H.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 08.05.2018; Elsevier
• Subjects: AAP; AAV; adeno-associated virus; Amino Acid Motifs; capsid; capsid assembly; Capsid Proteins - chemistry; Capsid Proteins - metabolism; Dependovirus - pathogenicity; Dependovirus - physiology; Dependovirus - ultrastructure; Gain of Function Mutation; gene therapy; HEK293 Cells; Human health and pathology; Humans; Life Sciences; manufacturing; Models, Molecular; Phenotype; Phylogeny; Protein Binding; Protein Multimerization; Protein Stability; Serotyping; structure-function; vector engineering; Virion - pathogenicity; Virion - ultrastructure; Virus Assembly; AAP; AAV; capsid assembly; capsid; manufacturing; structure-function; gene therapy; adeno-associated virus; vector engineering; vector; engineering
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2018.04.026

The adeno-associated virus (AAV) vector is a preferred delivery platform for in vivo gene therapy. Natural and engineered variations of the AAV capsid affect a plurality of phenotypes relevant to gene therapy, including vector production and host tropism. Fundamental to these aspects is the mechanism of AAV capsid assembly. Here, the role of the viral co-factor assembly-activating protein (AAP) was evaluated in 12 naturally occurring AAVs and 9 putative ancestral capsid intermediates. The results demonstrate increased capsid protein stability and VP-VP interactions in the presence of AAP. The capsid’s dependence on AAP can be partly overcome by strengthening interactions between monomers within the assembly, as illustrated by the transfer of a minimal motif defined by a phenotype-to-phylogeny mapping method. These findings suggest that the emergence of AAP within the Dependovirus genus relaxes structural constraints on AAV assembly in favor of increasing the degrees of freedom for the capsid to evolve. [Display omitted] •Dependence on AAP for capsid assembly varies widely across 21 AAV variants•AAP-dependent capsid proteins are subject to multiple rapid degradation pathways•AAP promotes interactions between capsid proteins•Specific capsid residues at trimer interface influence dependence on AAP Maurer et al. describe a phenotype-to-phylogeny mapping strategy correlating phenotypic variation in AAVs to a reconstructed phylogeny, revealing capsid structure-function relationships relevant to that phenotype. Dependence on the viral co-factor AAP for capsid assembly is examined, and capsid functional motifs, in addition to mechanistic roles of AAP, are elucidated.