Endocytosis of hyaluronidase-1 by the liver

Marie-Christine Gasingirwa , Jacqueline Thirion , Jeannine Mertens-Strijthagen , Simone Wattiaux-de Coninck , Bruno Flamion , Robert Wattiaux (1) , Michel Jadot

1 Physiological Chemistry

It has been suggested that intracellular hyaluronidase-1 (Hyal-1), considered as a lysosomal enzyme, originates from the endocytosis of the serum enzyme. To check this proposal we have investigated the uptake of recombinant human hyaluronidase-1 (rhHyal-1) by mouse liver and its intracellular distribution, making use of centrifugation methods. Experiments were performed on wild type mice injected with 125I-rhHyal-1 and on null mice (Hyal-1 -/-) injected with the unlabelled enzyme. Mice were euthanized at increasing times after injection Activity of the unlabelled enzyme was determined by zymography. Intracellular distribution of the Hyal-1 was investigated by differential and isopycnic centrifugation. Results indicated that rhHyal-1 is endocytosed by the liver, mainly by sinusoidal cells and follows the intracellular pathway described for many endocytosed proteins that find themselves eventually in lysosomes. However, Hyal-1 endocytosis has some particular features. Endocytosed rhHyal-1 is quickly degraded. Its distribution after differential centrifugation differs from the distribution of β-galactosidase, taken as reference enzyme of lysosomes. After isopycnic centrifugation in a sucrose gradient, endocytosed rhHyal-1 behaves like β-galactosidase soon after injection but Hyal-1 distribution is markedly less affected than the distribution of β-galactosidase by a prior injection of Triton WR-1339 to the mice. This agent is a specific density perturbant of lysosomes. Behaviour in centrifugation of endogenous liver Hyal-1, identified by HA zymography exhibits some kinship with the behaviour of the endocytosed enzyme, suggesting that it could originate from an endocytosis of the serum enzyme. Overall, these results could be explained by supposing that active endocytosed Hyal-1 is mainly present in early lysosomes. Although its degradation half-time is short, Hyal-1 could exert its activity owing to a constant supply of active molecules from the blood.

Mots clés: Life Sciences

Marie-Christine Gasingirwa, Jacqueline Thirion, Jeannine Mertens-Strijthagen, Simone Wattiaux-de Coninck, Bruno Flamion, et al.. Endocytosis of hyaluronidase-1 by the liver. Biochemical Journal, 2010, 430 (2), pp.305-313. ⟨10.1042/BJ20100711⟩. ⟨hal-00509883⟩