Hyaluronidase Hyal1 increases tumor cell proliferation and motility through accelerated vesicle trafficking [Molecular Bases of Disease]

April 8th, 2015 by McAtee, C. O., Berkebile, A. R., Elowsky, C., Fangman, T., Barycki, J. J., Wahl, J. K., Khalimonchuk, O., Naslavsky, N., Caplan, S., Simpson, M. A.

Hyaluronan turnover accelerates metastatic progression of prostate cancer partly by increasing rates of tumor cell proliferation and motility. To determine the mechanism, we overexpressed Hyal1 as a fluorescent fusion protein and examined its impact on endocytosis and vesicular trafficking. Overexpression of Hyal1 led to increased rates of internalization of hyaluronan and the endocytic recycling marker transferrin. Live imaging of Hyal1, sucrose gradient centrifugation, and specific co-localization of Rab GTPases defined the subcellular distribution of Hyal1 as early and late endosomes, lysosomes, and recycling vesicles. Manipulation of vesicular trafficking by chemical inhibitors or with constitutively active and dominant negative Rab expression constructs, caused atypical localization of Hyal1. Using the catalytically inactive point mutant Hyal1-E131Q, we found enzymatic activity of Hyal1 was necessary for normal localization within the cell, as Hyal1-E131Q was mainly found within the ER. Expression of a hyaluronan-binding point mutant Hyal1-Y202F revealed that secretion of Hyal1 and concurrent reuptake from the extracellular space is critical for rapid hyaluronan internalization and cell proliferation. Overall, excess Hyal1 secretion accelerates endocytic vesicle trafficking in a substrate-dependent manner, which promotes aggressive tumor cell behavior.