The structural organisation of pentraxin-3 and its interactions with heavy chains of inter-α-inhibitor regulate crosslinking of the hyaluronan matrix

Matrix Biology, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 1, 2025

Pentraxin-3 (PTX3) is an octameric protein, comprised of eight identical protomers, that has diverse functions in reproductive biology, innate immunity and cancer. PTX3 interacts with the large polysaccharide hyaluronan (HA) to which heavy chains (HCs) inter-α-inhibitor (IαI) family proteoglycans are covalently attached, playing a key role (non-covalent) crosslinking HC•HA complexes. These interactions stabilise cumulus matrix, essential for ovulation fertilisation mammals, also implicated formation pathogenic matrices context viral lung infections. To better understand physiological pathological roles we have analysed how its quaternary structure underpins HA via HCs. A combination X-ray crystallography, cryo-electron microscopy (cryo-EM) AlphaFold predictive modelling revealed C-terminal pentraxin domains octamer arranged central cube, two long extensions on either side, each formed from four protomers assembled into tetrameric coiled-coil regions, essentially as described by (Noone et al., 2022; doi:10.1073/pnas.2208144119). From crystallography cryo-EM data, identified network inter-protomer salt bridges facilitate assembly octamer. Small angle scattering (SAXS) validated our model including analysis constructs: 'Half-PTX3' construct missing 24 N-terminal residues (Δ1-24-PTX3). SAXS determined length ∼520 Å and, combined 3D variability defined flexibility extensions. Biophysical analyses prototypical chain HC1 does not interact at pH 7.4, consistent previous studies showing that, this pH, only associates complexes if they presence. However, binds acidic can be incorporated pre-formed under these conditions. This provides novel mechanism regulation PTX3-mediated (e.g., during inflammation), likely mediated pH-dependent conformational change HC1. The was found associate simultaneously up molecules thus, potential form major node within matrices, i.e., where physical biochemical properties resulting could tuned HC/PTX3 composition.

Language: Английский

Oligomerisation of pentraxin-3: insights from cryoEM

Matrix Biology, Journal Year: 2025, Volume and Issue: unknown

Published: April 1, 2025

Language: Английский