Mouse liver lysosomes contain enzymatically active processed forms of Hyal-1 |
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Authors: | Marielle Boonen Emeline Puissant Florentine Gilis Bruno Flamion Michel Jadot |
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Institution: | 1. URPhyM-Laboratoire de Chimie Physiologique, Narilis, University of Namur, 61 rue de Bruxelles, 5000 Namur, Belgium;2. URPhyM-Laboratoire de Physiologie et Pharmacologie, Narilis, University of Namur, 61 rue de Bruxelles, 5000 Namur, Belgium |
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Abstract: | It has long been known that liver lysosomes contain an endoglycosidase activity able to degrade the high molecular mass glycosaminoglycan hyaluronic acid (HA). The identification and cloning of a hyaluronidase with an acidic pH optimum, Hyal-1, suggested it might be responsible for this activity. However, we previously reported that this hydrolase could only be detected in pre-lysosomal compartments of the mouse liver using a zymography technique that allows the detection of Hyal-1 activity after SDS–PAGE (“renatured protein zymography”). Present work reveals that the activity highlighted by this technique belongs to a precursor form of Hyal-1 and that the lysosomal HA endoglycosidase activity of the mouse liver is accounted for by a proteolytically processed form of Hyal-1 that can only be detected using “native protein zymography”. Indeed, the distribution of this form follows the distribution of β-galactosidase, a well-established lysosomal marker, after fractionation of the mouse liver in a linear sucrose density gradient. In addition, both activities shift toward the lower density region of the gradient when a specific decrease of the lysosomal density is induced by Triton WR-1339 injection. The fact that only native protein zymography but not renatured protein zymography is able to detect Hyal-1 activity in lysosomes points to a non-covalent association of Hyal-1 proteolytic fragments or the existence of closely linked partners supporting Hyal-1 enzymatic activity. The knockdown of Hyal-1 results in an 80% decrease of total acid hyaluronidase activity in the mouse liver, confirming that Hyal-1 is a key actor of HA catabolism in this organ. |
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Keywords: | DMAB p-dimethylaminobenzaldehyde ER endoplasmic reticulum GPI glycophosphatidylinositol HA hyaluronic acid Hyal-1 hyaluronidase-1 RSA relative specific activity |
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