Mapping of Adenovirus of serotype 3 fibre interaction to desmoglein 2 revealed a novel ‘non-classical’ mechanism of viral receptor engagement

Abstract

High-affinity binding of the trimeric fibre protein to a cell surface primary receptor is a common feature shared by all adenovirus serotypes. Recently, a long elusive species B adenovirus receptor has been identified. Desmoglein 2 (DSG2) a component of desmosomal junction, has been reported to interact at high affinity with Human adenoviruses HAd3, HAd7, HAd11 and HAd14. Little is known with respect to the molecular interactions of adenovirus fibre with the DSG2 ectodomain. By using different DSG2 ectodomain constructs and biochemical and biophysical experiments, we report that the third extracellular cadherin domain (EC3) of DSG2 is critical for HAd3 fibre binding. Unexpectedly, stoichiometry studies using multi-angle laser light scattering (MALLS) and analytical ultra-centrifugation (AUC) revealed a non-classical 1:1 interaction (one DSG2 per trimeric fibre), thus differentiating ‘DSG2-interacting’ adenoviruses from other protein receptor interacting adenoviruses in their infection strategy.

Cryo-EM structure of adenovirus type 3 fibre with desmoglein 2 shows a novel mode of receptor engagement

“…Whether one or two receptors are bound, both EC2 and EC3 domains are involved in the interaction (Figure 2a-b, Supplementary Figure S2.a-b) . This observation is in agreement with the biochemical data reporting that EC3 is critical for HAd3K binding while EC2 stabilizes this interaction 6 . Several residues distributed along the EC2 primary sequence were found to interact with the HAd3K monomer A, while only one region in EC3 (covering residues 313 to 321) is involved in the interaction with the groove of monomer B (Figure 2c).…”

“…The structural data provided here exclude again the three-receptor per knob scenario . The 1:1 (receptor:knob) binding strategy is more in agreement with both the statistical data (Supplementary Table1) and with our previously biochemical study 6 . Of note, multimerization of the trimeric HAd3K is necessary to cluster enough DSG2 molecules for intracellular signaling that leads to junction opening 10,11 .…”

“…The location of only one EC2-EC3 close to the three-fold axis is unusual as compared to CD46 and CAR for which three receptors were found at the periphery of the fibre knob. Moreover, different population of particles with either one or two EC2-EC3 modules (HAd3K / EC2-EC3 and HAd3K / (EC2-EC3)2) were identifiable (Supplementary Figure S1.a-c) in agreement with the 5,40S and 7,34S species previously reported 6 . The 3D structures were solved to an overall resolution of 3.5 and 3.8 Å, respectively.…”

“…The intermediate portion of the DSG2 ectodomain, consisting of EC2 and EC3, has been described as important for recognition by the HAd3 knob (HAd3K), the trimeric globular distal part of the fibre protein. HAd3K binds to DSG2 by non-classical mechanism involving mainly one receptor bound per trimeric fibre knob resulting in a sedimentation coefficient of 5.40S corresponding to a 96kDa complex 6 .…”

The fiber knob protein of human adenovirus type 49 mediates highly efficient and promiscuous infection of cancer cell lines using a novel cell entry mechanism

“…Therefore, in the presence of CAR the recombinant fiber knob would be sequestered on the higher affinity CAR receptor leaving the alternative receptor free to interact with the virus. A low affinity receptor would also, likely, depend upon avidity, so might not be observed with single trimers of HAdV-D49K; a similar effect has previously been observed with HAdV-B3K and DSG2 (38) and CD46 (39). This is supported by the observation what HAdV-D49K cannot transduce cells as efficiently when incubated on ice in the absence of CAR, while HAdV-C5 and HAdV-C5/B35K, which form high affinity receptor interactions, are unencumbered ( Figure 2).…”