Progranulin Stimulates the In Vitro Maturation of Pro-Cathepsin D at Acidic pH. Issue 5 (1st March 2019)

• Record Type: Journal Article
• Authors: Butler, Victoria J.; Cortopassi, Wilian A.; Argouarch, Andrea R.; Ivry, Sam L.; Craik, Charles S.; Jacobson, Matthew P.; Kao, Aimee W.
• Is Part Of: Journal of molecular biology. Volume 431:Issue 5(2019)
• Page Start: 1038
• Page End: 1047
• Publication Date: 2019-03-01
• Subjects: progranulin -- cathepsin D -- maturation -- propeptide -- neurodegeneration; PGRN progranulin -- CTSD cathepsin D -- DSF differential scanning fluorimetry; Molecular biology -- Periodicals; Biology -- Periodicals; Biochemistry -- Periodicals; Bacteriology -- Periodicals; Molecular Biology -- Periodicals; Biochemistry -- Periodicals; Biologie moléculaire -- Périodiques; Biologie -- Périodiques; Biochimie -- Périodiques; Moleculaire biologie; Biochemistry; Biology; Molecular biology; Periodicals; 572.805
• DOI: 10.1016/j.jmb.2019.01.027
• Languages: English
• ISSNs: 0022-2836

Abstract

Abstract: Single-copy loss-of-function mutations in the progranulin gene ( PGRN ) underlie the neurodegenerative disease frontotemporal lobar degeneration, while homozygous loss-of-function of PGRN results in the lysosomal storage disorder neuronal ceroid lipofuscinosis. Despite evidence that normal PGRN levels are critical for neuronal health, the function of this protein is not yet understood. Here, we show that PGRN stimulates the in vitro maturation of the lysosomal aspartyl protease cathepsin D (CTSD). CTSD is delivered to the endolysosomal system as an inactive precursor (proCTSD) and requires sequential cleavage steps via intermediate forms to achieve the mature state (matCTSD). In co-immunoprecipitation experiments, PGRN interacts predominantly with immature pro- and intermediate forms of CTSD. PGRN enhances in vitro conversion of proCTSD to matCTSD in a concentration-dependent manner. Differential scanning fluorimetry shows a destabilizing effect induced by PGRN on proCTSD folding (∆ T m = − 1.7 °C at a 3:1 molar ratio). We propose a mechanism whereby PGRN binds to proCTSD, destabilizing the propeptide from the enzyme catalytic core and favoring conversion to mature forms of the enzyme. Further understanding of the role of PGRN in CTSD maturation will assist in the development of targeted therapies for neurodegenerative disease. Graphical abstract: Proposed model for the role of progranulin (PGRN) in pro-cathepsin D (proCTSD) maturation. (A) ProCTSD undergoes an autocatalytic activation mechanism for the formation of initial matCTSD molecules at a low rate. (B) Once formed, matCTSD can convert proCTSD to matCTSD through an intermolecular cleavage of the propeptide. (C) PGRN binds around the propeptide region of proCTSD to destabilize its interaction with the enzyme catalytic core, (D) facilitating propeptide cleavage by matCTSD. Catalytic aspartyl residues are represented as orange dots, the propeptide in blue, and the propeptide cleavage site in red. Unlabelled Image Highlights: Interaction of progranulin and pro-cathepsin D was investigated in vitro. Progranulin binds to pro- and intermediate forms of cathepsin D in co-immunoprecipitation experiments. Progranulin stimulates the maturation of pro-cathepsin D to its mature form in vitro at acidic pH. We propose a kinetic model for the stimulation of pro-cathepsin D maturation by progranulin, involving destabilization of the cathepsin D propeptide.