Vaspin identified as a DNA-binding serpin with functional consequences for protease inhibition

Area of Science:

• Biochemistry
• Molecular Biology
• Protease Inhibition

Background:

• Vaspin is a serpin (serine protease inhibitor) expressed in various tissues, including skin, liver, and adipose tissue.
• It plays a role in counteracting inflammation and oxidative stress in conditions like inflammatory skin diseases and obesity.
• Vaspin inhibits kallikrein proteases KLK7 and KLK14 and binds to the low-density lipoprotein receptor-related protein 1 (LRP1).

Purpose of the Study:

• To investigate the potential DNA-binding properties of vaspin, prompted by its intracellular localization and known binding to heparin and polyphosphates.
• To determine if DNA influences vaspin's protease inhibitory activity.
• To characterize the DNA-binding site on vaspin.

Main Methods:

• DNA-affinity chromatography and differential radial capillary action of ligand assays were employed to assess DNA binding.
• The crystal structure of polyphosphate-bound vaspin was determined.
• Mutagenesis was used to create a non-heparin-binding (NHB) vaspin variant to study DNA binding and function.

Main Results:

• Vaspin exhibits high-affinity binding to both single- and double-stranded DNA.
• DNA significantly accelerates vaspin's inhibition of KLK7.
• A non-heparin-binding vaspin mutant retained high-affinity DNA binding and accelerated protease inhibition, suggesting DNA binding is independent of the heparin-binding site.

Conclusions:

• Vaspin is identified as the second human serpin with DNA-binding capabilities.
• This DNA interaction likely contributes to vaspin's nuclear localization and may mediate intracellular functions.
• The nonspecific DNA binding accelerates protease inhibition, suggesting a novel mechanism for vaspin's biological activity.