Application of reverse transcription–PCR to total RNA prepared from TNF-α (tumour necrosis factor-α)-stimulated HUVECs (human umbilical vein endothelial cells) revealed that the syndecan-2 mRNA was up-regulated by this inflammatory stimulus. By immunoprecipitation using an anti-syndecan-2 antibody on TNF-α-stimulated HUVEC lysates, inflammation-induced interleukin-8 was found to be an interaction partner of this HS (heparan sulphate) proteoglycan, but not of any other syndecan on these cells. The glycosylated [Syn2ect(+HS)] and non-glycosylated [Syn2ect(−HS)] forms of Syn2ect (the syndecan-2 ectodomain) were purified from a stably transfected human cell line and from a bacterial expression system respectively. By CD spectroscopy, Syn2ect was found to adopt an all-β secondary structure. The dissociation constant of Syn2ect(+HS) with respect to interleukin-8 binding was determined by isothermal fluorescence titrations to be 23 nM. Despite its lack of HS chains, Syn2ect(−HS) exhibited significant binding to the chemokine, with a Kd of >1 µM. Thus, in addition to glycosaminoglycan binding, protein–protein contacts might also contribute to the chemokine–proteoglycan interaction.
- heparan sulphate
↵1 These authors have contributed equally to this work.
Abbreviations used: DMEM, Dulbecco's modified Eagle's medium; GAG, glycosaminoglycan; GST, glutathione S-transferase; HS, heparan sulphate; HSPG, heparan sulphate proteoglycan; HUVEC, human umbilical vein endothelial cell; IL-8, interleukin-8; RT-PCR, reverse transcription–PCR; Syn2ect, ectodomain of syndecan-2; Syn2ect(+HS), glycosylated form of Syn2ect; Syn2ect(−HS), non-glycosylated form of Syn2ect; TNF-α, tumour necrosis factor-α.
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