Biology subjects

DiMaio, D.

Publications and source records attributed to DiMaio, D..

10 recordsLinked to original sources

bioRxiv2026

The human papillomavirus L2 protein in the capsid is an ensemble of related structures poised to exit the virus particle

The human papillomavirus (HPV) capsid contains 360 molecules of the L1 protein, which assembles into pentamers that form the capsid shell, and up to 72 molecules of the L2 protein. The C-terminus of the L2 protein must emerge from the capsid, insert into the endosome membrane, and protrude into the cytoplasm to bind to cellular proteins that mediate trafficking of the virus to the nucleus during virus entry. Computational analysis predicts that much of L2 is disordered, but the stoichiometry, structure and location of L2 in the capsid remain elusive. Here, we use cryo-EM single particle analysis of HPV16 pseudovirus capsids with and without the L2 protein combined with AlphaFold3 predictions and molecular dynamics simulations to develop a structural model of L2 within the capsid. Our results revealed that a single molecule of L2 associates with the inner surface of most L1 pentamers. The relatively rigid structure of the pentamer forces the long intrinsically disordered segments of L2 to adopt numerous related, compact, stable conformations in the capsid, whereas the structured elements of L2 remain folded but adopt varied positions in space largely beneath the pentamer. A finger-like projection of L2 extends into the central pore of the pentamer, but many different segments of the disordered domains of L2 can form fingers. In some models the C-terminus of L2 extends through the pore to the exterior surface of the capsid positioned to insert into the endosomal membrane. Consistent with these models, analysis of purified pseudoviruses showed that the C-terminus of multiple L2 molecules is exposed on the surface of each capsid. These findings provide a structural basis for understanding how L2 is organized in the capsid poised to initiate its action during virus entry.

microbiology↗

bioRxiv2026

Cargo-Adaptor Cooperation Programs Retromer Coat Architecture

Retromer drives endosomal cargo retrieval in combination with sorting nexin (SNX) adaptors, but how adaptor-cargo combinations specify coat architecture remains unclear. We identify sorting nexin 12 (SNX12) as the retromer adaptor required for human papillomavirus 16 (HPV16) infection and show that the viral L2 capsid protein tail directly engages SNX12-retromer complexes to trigger membrane tubulation. The crystal structure reveals a conserved cargo-recognition mode, whereas cryo-electron tomography of reconstituted assemblies shows retromer arches organized into two lattice configurations stabilized by membrane-proximal interfaces. These lattices assemble as multi-start helices and accommodate curvature through hinge-like motions between arches. These findings establish cargo and adaptor identity as co-determinants of retromer coat architecture, revealing retromer as a programmable system capable of generating route-specific transport carriers.

cell biology↗

bioRxiv2025

Pancreatic cancer cachexia is mediated by PTHrP-driven disruption of adipose de novo lipogenesis

Pancreatic cancer patients have the highest rates and most severe forms of cancer cachexia, yet cachexia etiologies remain largely elusive, leading to a lack of effective intervening therapies. Parathyroid hormone-related protein (PTHrP) has been clinically implicated as a putative regulator of cachexia, with serum PTHrP levels correlating with increased weight loss in PDAC patients. Here we show that cachectic PDAC patients have high expression of tumor PTHrP and use a genetically engineered mouse model to functionally demonstrate that loss of PTHrP blocks cachectic wasting, dramatically extending overall survival. The re-expression of PTHrP in lowly cachectic models is sufficient to induce wasting and reduce survival in mice, which is reversed by the conditional deletion of the PTHrP receptor, Pth1r, in adipocytes. Mechanistically, tumor-derived PTHrP suppresses de novo lipogenesis in adipocytes, leading to a molecular rewiring of adipose depots to promote wasting in the cachectic state. Finally, the pharmacological disruption of the PTHrP-PTH1R signaling axis abrogates wasting, highlighting that a targeted disruption of tumor-adipose crosstalk is an effective means to limit cachexia. STATEMENT OF SIGNIFICANCEPancreatic ductal adenocarcinoma (PDAC) is the prototypical cancer type associated with cancer cachexia, a debilitating wasting syndrome marked by adipose tissue loss and muscle atrophy. Herein, we establish that PTHrP is a tumor-derived factor that facilitates cachexia by downregulating de novo lipogenesis in adipocytes and that blocking PTHrP is an effective means to limit wasting in preclinical mouse models.

cancer biology↗

bioRxiv2025

Golgi-associated nuclear import receptor importin-7 targets HPV from the Golgi to the nucleus to promote infection

During human papillomavirus (HPV) entry, the virus exploits COPI-dependent retrograde transport to cross the trans-Golgi network and Golgi stacks before reaching the nucleus to cause infection. How HPV enters the nucleus after exiting the Golgi is unclear, although mitotic nuclear envelop breakdown (NEB) appears important. Here we show that importin-7 (IPO7), a nuclear pore import receptor, associates with the Golgi and promotes HPV infection. Upon IPO7 knockdown, HPV infection is inhibited and the virus accumulates in the Golgi but does not enter the nucleus, demonstrating that IPO7 promotes Golgi-to-nucleus transport of HPV. We further reveal that the C-terminus of HPV capsid protein L2, which is thought to contain overlapping nuclear localization and cell-penetrating peptide sequences, binds directly to IPO7 in a step that requires COPI-dependent virus trafficking. Together these data identify a role of an importin in HPV infection, raising the possibility that the canonical nuclear pore import machinery plays an unanticipated role in NEB-dependent nuclear entry. TeaserHPV, a cancer-causing human pathogen, exploits the Golgi-associated nuclear import receptor IPO7 for Golgi-to-nucleus trafficking to promote infection.

cell biology↗

bioRxiv2024

γ-secretase facilitates retromer-mediated retrograde transport

The retromer complex mediates retrograde transport of protein cargos from endosomes to the trans-Golgi network (TGN). {gamma}-secretase is a multisubunit protease that cleaves the transmembrane domain of its target proteins. Mutations in genes encoding subunits of retromer or {gamma}-secretase can cause familial Alzheimer disease (AD) and other degenerative neurological diseases. It has been reported that retromer interacts with {gamma}-secretase, but the consequences of this interaction are not known. Here, we report that retromer-mediated retrograde protein trafficking in cultured human epithelial cells is impaired by inhibition of {gamma}-secretase activity or by genetic elimination of {gamma}-secretase. {gamma}-secretase inhibitor XXI and knockout of PS1, the catalytic subunit of {gamma}-secretase, inhibit endosome to TGN trafficking of retromer-dependent retrograde cargos, divalent metal transporter 1 isoform II (DMT1-II), cation-independent mannose-6-phosphate receptor (CIMPR), and shiga toxin. Trafficking of retromer-independent cargos, such as cholera toxin and a CIMPR mutant that does not bind to retromer was not affected by {gamma}-secretase inhibition. XXI treatment and PS1 KO inhibit interaction of {gamma}-secretase with retromer but do not inhibit the association of cargo with retromer or with {gamma}-secretase in intact cells. Similarly, these treatments do not affect the level of Rab7-GTP, which regulates retromer-cargo interaction. These results suggest that the {gamma}-secretase-retromer interaction facilitates retromer-mediated retrograde trafficking.

cell biology↗

bioRxiv2024

Rab6a enables BICD2/dynein-mediated trafficking of human papillomavirus from the trans-Golgi network during virus entry

Rab GTPases control intracellular vesicular transport, including retrograde trafficking of human papillomavirus (HPV) during cell entry, guiding the virus from the endosome to the trans-Golgi network (TGN), the Golgi apparatus, and eventually the nucleus. Rab proteins that act prior to the arrival of HPV to the TGN have been identified, but Rab proteins operating in later stages of entry remain elusive. Here, we report that knockdown of Rab6a impairs HPV entry by impeding intra-Golgi transport of the incoming virus, resulting in HPV accumulation in the TGN. Rab6a supports HPV trafficking by facilitating the association of HPV with dynein, a motor protein complex, and BICD2, a dynein adaptor. L2 can bind directly to GTP-Rab6a in vitro, and excess of either GTP-Rab6a or GDP-Rab6 inhibits HPV entry, suggesting that cycling between GDP- Rab6 and GTP-Rab6 is critical. Notably, Rab6a is crucial for HPV-BICD2 and HPV-dynein association in the TGN of infected cells, but the HPV-dynein association in the endosome does not require Rab6a. Our findings reveal an important feature of the molecular basis of intra-Golgi trafficking of HPV and identify potential targets for therapeutic approaches to inhibit HPV infection.

microbiology↗

bioRxiv2023

Noncanonical Rab9a action supports endosomal exit of human papillomavirus during virus entry

Rab GTPases play key roles in controlling intracellular vesicular transport. GTP-bound Rab proteins support vesicle trafficking. Here, we report that, unlike cellular protein cargos, the delivery of human papillomaviruses (HPV) into the retrograde transport pathway during virus entry is inhibited by Rab9a in its GTP-bound form. Knockdown of Rab9a hampers HPV entry by regulating the HPV-retromer interaction and impairing retromer-mediated endosome-to-Golgi transport of the incoming virus, resulting in the accumulation of HPV in the endosome. Rab9a is in proximity to HPV as early as 3.5 h post-infection, prior to the Rab7-HPV interaction. HPV displays increased association with retromer in Rab9a knockdown cells, even in the presence of dominant negative Rab7. Thus, Rab9a can regulate HPV-retromer association independently of Rab7. Surprisingly, excess GTP-Rab9a impairs HPV entry, whereas excess GDP-Rab9a stimulates entry. These findings reveal that HPV employs a trafficking mechanism distinct from that used by cellular proteins.

microbiology↗

bioRxiv2023

Sequence independent activity of a predicted long disordered segment of the human papillomavirus L2 capsid protein during virus entry

The papillomavirus L2 capsid protein protrudes through the endosome membrane into the cytoplasm during virus entry to bind cellular factors required for intracellular virus trafficking. Cytoplasmic protrusion of HPV16 L2, virus trafficking, and infectivity are inhibited by large deletions in an [~]110 amino acid segment of L2 that is predicted to be disordered. The activity of these mutants can be restored by inserting protein segments with diverse compositions and chemical properties into this region, including scrambled sequences, a tandem array of a short sequence, and the intrinsically disordered region of a cellular protein. The infectivity of mutants with small in-frame insertions and deletions in this segment directly correlates with the size of the segment. These results indicate that the length of the disordered segment, not its sequence or its composition, determines its activity during virus entry. Sequence independent but length dependent activity has important implications for protein function and evolution.

biochemistry↗

bioRxiv2023

Designed Transmembrane Proteins Inhibit the Erythropoietin Receptor in a Custom Binding Topology

Transmembrane (TM) domains as simple as a single span can perform complex biological functions using entirely lipid-embedded chemical features. Computational design has potential to generate custom tool molecules directly targeting membrane proteins at their functional TM regions. Thus far, designed TM domain-targeting agents have been limited to mimicking binding modes and motifs of natural TM interaction partners. Here, we demonstrate the design of de novo TM proteins targeting the erythropoietin receptor (EpoR) TM domain in a custom binding topology competitive with receptor homodimerization. The TM proteins expressed in mammalian cells complex with EpoR and inhibit erythropoietin-induced cell proliferation. In vitro, the synthetic TM domain complex outcompetes EpoR homodimerization. Structural characterization reveals that the complex involves the intended amino acids and agrees with our designed molecular model of antiparallel TM helices at 1:1 stoichiometry. Thus, membrane protein TM regions can now be targeted in custom designed topologies.

bioengineering↗

bioRxiv2018

SV40 polyomavirus activates the Ras-MAPK signaling pathway for vacuolization, cell death, and virus release

Polyomaviruses are a family of small, non-enveloped DNA viruses that can cause severe disease in immunosuppressed individuals. Studies with SV40, a well-studied model polyomavirus, have revealed the role of host proteins in polyomavirus entry and trafficking to the nucleus, viral transcription and DNA replication, and cell transformation. In contrast, little is known about host factors or cellular signaling pathways involved in the late steps of productive infection leading to polyomavirus release. We previously showed that cytoplasmic vacuolization, a characteristic late cytopathic effect of SV40, depends on the specific interaction between the major viral capsid protein VP1 and its cell surface ganglioside receptor GM1. Here we show that late during infection, SV40 activates a signaling cascade in permissive CV-1 monkey cells involving Ras, Rac1, MKK4 and JNK to induce SV40-specific cytoplasmic vacuolization and subsequent cell lysis and virus release. Inhibition of individual components of this signaling pathway inhibits vacuolization, lysis and virus release, even though high-level intracellular virus replication occurs. The identification of this pathway for SV40-induced vacuolization and virus release provides new insights into the late steps of non-enveloped virus infection and reveals potential drug targets for the treatment of diseases caused by these viruses.\n\nIMPORTANCEThe polyomaviruses are small DNA viruses that include important model viruses and human pathogens that can cause fatal disease, including cancer, in immunosuppressed individuals. There are no vaccines or specific antiviral agents for any polyomavirus. Here, we show that late during infection, SV40 activates a signaling cascade involving Ras, Rac, and JNK that is required for cytoplasmic vacuolization and efficient virus release. This pathway may represent a new point of intervention to control infection by these viruses.

microbiology↗