title: Fully reduced granulin-B is intrinsically disordered and displays concentration-dependent dynamics.
abstract: Granulins (Grns) are a family of small, cysteine-rich proteins that are generated upon proteolytic cleavage of their precursor, progranulin (Pgrn). All seven Grns (A-G) contain 12 conserved cysteines that form 6 intramolecular disulfide bonds, rendering this family of proteins unique. Grns are known to play multi-functional roles, including wound healing, embryonic growth, and inflammation and are implicated in neurodegenerative diseases. Despite their manifold functions, there exists a dearth of information regarding their structure-function relationship. Here, we sought to establish the role of disulfide bonds in promoting structure by investigating the fully reduced GrnB (rGrnB). We report that monomeric rGrnB is an intrinsically disordered protein (IDP) at low concentrations. rGrnB undergoes dimerization at higher concentrations to form a fuzzy complex without a net gain in the structure-a behavior increasingly identified as a hallmark of some IDPs. Interestingly, we show that rGrnB is also able to activate NF-κB in human neuroblastoma cells in a concentration-dependent manner. This activation correlates with the observed monomer-dimer dynamics. Collectively, the presented data establish that the intrinsic disorder of rGrnB governs conformational dynamics within the reduced form of the protein, and suggest that the overall structure of Grns could be entirely dictated by disulfide bonds.
authors.affiliation: Department of Chemistry and Biochemistry, University of Southern Mississippi, Hattiesburg, MS 39406, USA.
authors.forename: Gaurav
authors.initials: G
authors.lastname: Ghag
authors.affiliation: Biomedical Engineering Program and.
authors.forename: Lauren M
authors.initials: LM
authors.lastname: Wolf
authors.affiliation: Department of Chemistry and Biochemistry, University of Southern Mississippi, Hattiesburg, MS 39406, USA.
authors.forename: Randi G
authors.initials: RG
authors.lastname: Reed
authors.affiliation: Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208, USA.
authors.forename: Nicholas P
authors.initials: NP
authors.lastname: Van Der Munnik
authors.affiliation: Institute of Molecular Biophysics, Florida State University, Tallahassee, FL 32306, USA.
authors.forename: Claudius
authors.initials: C
authors.lastname: Mundoma
authors.affiliation: Biomedical Engineering Program and Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208, USA.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Moss
authors.affiliation: Department of Chemistry and Biochemistry, University of Southern Mississippi, Hattiesburg, MS 39406, USA vijay.rangachari@usm.edu.
authors.forename: Vijayaraghavan
authors.initials: V
authors.lastname: Rangachari
mesh_terms: D045744:Cell Line, Tumor; D017124:Conserved Sequence; D000077155:Granulins; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000737:chemistry* / Q000378:metabolism*; D064267:Intrinsically Disordered Proteins / Q000737:chemistry* / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D010084:Oxidation-Reduction; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary
chemical_list: D000077155:Granulins; D036341:Intercellular Signaling Peptides and Proteins; D064267:Intrinsically Disordered Proteins; D016328:NF-kappa B
keywords: cysteine-rich protein; fuzzy complex; granulin; intrinsically disordered protein; progranulin