Dataset Information

Human paraneoplastic antigen Ma2 (PNMA2) forms icosahedral capsids that can be engineered for mRNA delivery.

ABSTRACT: A number of endogenous genes in the human genome encode retroviral gag-like proteins, which were domesticated from ancient retroelements. The paraneoplastic Ma antigen (PNMA) family members encode a gag-like capsid domain, but their ability to assemble as capsids and traffic between cells remains mostly uncharacterized. Here, we systematically investigate human PNMA proteins and find that a number of PNMAs are secreted by human cells. We determine that PNMA2 forms icosahedral capsids efficiently but does not naturally encapsidate nucleic acids. We resolve the cryoelectron microscopy (cryo-EM) structure of PNMA2 and leverage the structure to design engineered PNMA2 (ePNMA2) particles with RNA packaging abilities. Recombinantly purified ePNMA2 proteins package mRNA molecules into icosahedral capsids and can function as delivery vehicles in mammalian cell lines, demonstrating the potential for engineered endogenous capsids as a nucleic acid therapy delivery modality.

SUBMITTER: Madigan V

PROVIDER: S-EPMC10945824 | biostudies-literature | 2024 Mar

REPOSITORIES: biostudies-literature

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Human paraneoplastic antigen Ma2 (PNMA2) forms icosahedral capsids that can be engineered for mRNA delivery.

Madigan Victoria V Zhang Yugang Y Raghavan Rumya R Wilkinson Max E ME Faure Guilhem G Puccio Elena E Segel Michael M Lash Blake B Macrae Rhiannon K RK Zhang Feng F

Proceedings of the National Academy of Sciences of the United States of America 20240304 11

A number of endogenous genes in the human genome encode retroviral <i>gag</i>-like proteins, which were domesticated from ancient retroelements. The paraneoplastic Ma antigen (PNMA) family members encode a <i>gag</i>-like capsid domain, but their ability to assemble as capsids and traffic between cells remains mostly uncharacterized. Here, we systematically investigate human PNMA proteins and find that a number of PNMAs are secreted by human cells. We determine that PNMA2 forms icosahedral capsi ...[more]

PMID: 38437549

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Project description:Anti-Ma2 encephalitis is a rare neurological disorder with a predominant involvement of brainstem, limbic and diencephalic structures. Although an unspecific encephalopathy is the usual form of presentation, acute-onset neurologic symptoms and other atypical manifestations have been described and account for the challenging diagnosis of this entity. Despite being usually detected as a paraneoplastic syndrome in patients with early-stage tumors or without a previous history of malignancy, a growing concern has arisen from several cases reported in metastatic patients under treatment with immune checkpoint inhibitors. We report what to our knowledge is the first known case of anti-Ma2 encephalitis associated to pembrolizumab and presenting as an acute-onset focal neurological syndrome, consisting on acute global aphasia, right upper limb paresia, hypoacusia, sleep disorder, decreased conscious level and a motor focal status that was refractory to anticonvulsant therapy. A brain MRI scan showed a focal alteration of the cortical-subcortical signal on the left parietal lobe. CSF study found a significant hyperproteinorrhachia and electroencephalography showed lateralized periodic discharges (LPDs), suggestive of a diffuse encephalopathy. A positive result for anti-Ma2 antibodies was obtained both in blood and CSF samples through indirect immune-fluorescence (IFI) and later confirmed by western-blot technique. Our patient obtained a mild response to steroid therapy and a significant improvement after the administration of intravenous immunoglobulins. The hypothesis that checkpoint inhibitors may trigger the expression of previously subclinical paraneoplastic events, through the strengthening of cytotoxic T cells-mediated immune response, is supported by our finding of preexisting anti-Ma2 antibodies in preserved blood samples obtained before the initiation of pembrolizumab in our patient. Further research is needed to reveal if the detection of onconeural antibodies prior to a treatment with checkpoint inhibitors may be used as a predictive biomarker of neurologic immune-related high-grade toxicity.

Project description:Spherical viruses are remarkably well characterized by the Triangulation (T) number developed by Casper and Klug. The T-number specifies how many viral capsid proteins are required to cover the virus, as well as how they are further subdivided into pentamer and hexamer subunits. The T-number however does not constrain the orientations of these proteins within the subunits or dictate where the proteins should place their protruding features. These protrusions often take the form of loops, spires and helices, and are significant because they aid in stability of the capsid as well as recognition by the host organism. Until now there has be no overall understanding of the placement of protrusions for spherical viruses, other than they have icosahedral symmetry. We constructed a set of gauge points based upon the work affine extensions of Keef and Twarock, which have fixed relative angular locations with which to measure the locations of these features. This work adds a new element to our understanding of the geometric arrangement of spherical viral capsid proteins; chiefly that the locations of protruding features are not found stochastically distributed in an icosahedral manner across the viral surface, but instead these features are found only in specific locations along the 15 icosahedral great circles. We have found that this result holds true as the T number and viral capsids size increases, suggesting an underlying geometric constraint on their locations. This is in spite of the fact that the constraints on the pentamers and hexamer orientations change as a function of T-number, as you need to accommodate more hexamers in the same solid angle between pentamers. The existence of this angular constraint of viral capsids suggests that there is a fitness or energetic benefit to the virus placing its protrusions in this manner. This discovery may have profound impacts on identifying and eliminating viral pathogens, understanding evolutionary constraints as well as bioengineering for capsid drug delivery systems. This result also suggests that in addition to biochemical attachment restrictions, there are additional geometric constraints that should be adhered to when modifying protein capsids.

Dataset Information

Human paraneoplastic antigen Ma2 (PNMA2) forms icosahedral capsids that can be engineered for mRNA delivery.

Publications

Human paraneoplastic antigen Ma2 (PNMA2) forms icosahedral capsids that can be engineered for mRNA delivery.

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