Glycobiology Advance Access originally published online on January 30, 2008
Glycobiology 2008 18(4):280-289; doi:10.1093/glycob/cwn006
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Mouse Hyal3 encodes a 45- to 56-kDa glycoprotein whose overexpression increases hyaluronidase 1 activity in cultured cells
3 Department of Biochemistry and Medical Genetics
4 Department of Physiology
5 Department of Pediatrics and Child Health, The University of Manitoba, 770 Bannatyne Ave., Winnipeg, MB R3E 0W3
6 Manitoba Institute for Child Health, 715 McDermot Ave., Winnipeg, MB R3E 3P4, Canada
1 To whom correspondence should be addressed: Tel: +1-204-789-3218; Fax: +1-204-789-3900; e-mail: traine{at}ms.umanitoba.ca
Received on April 3, 2007; revised on January 25, 2008; accepted on January 26, 2008
Hyaluronidases are enzymes that mediate the breakdown of hyaluronan (HA), a large polysaccharide abundant in the extracellular matrix of vertebrate tissues. Six genes have been predicted to encode hyaluronidases in humans, but the protein products of only SPAM1, HYAL1, and HYAL2 have been characterized. We have now expressed the mouse Hyal3 gene product, hyaluronidase 3 (Hyal3), in Baby Hamster Kidney (BHK) cells and demonstrated the presence of multiple forms of Hyal3 ranging from 
45 to 56 kDa in expression lysates. Complete and partial digestions of the expressed protein with PNGase F showed three N-linked oligosaccharides accounted for all forms of Hyal3 detected in expression lysates. Most of these oligosaccharides were Endo H sensitive, indicating that they were high mannose or hybrid N-linked oligosaccharides. Subcellular fractionation of Hyal3-expressing BHK cells by density gradient centrifugation revealed most Hyal3 in a low-density vesicular population. Low levels of Hyal3 were detected in higher density vesicles, but no colocalization with the late endosomal/lysosomal marker Lamp1 was found by immunofluorescence microscopy. BHK cells stably expressing Hyal3 had increased acid-active hyaluronidase activity, but no such activity was detected when Hyal3 was transfected into Hyaluronidase 1 (Hyal1)-deficient fibroblasts. Overexpression of Hyal3 in BHK cells increased the Hyal1 protein and mRNA levels, suggesting that the increased hyaluronidase activity in these cells was due to Hyal1 rather than Hyal3. The results indicate that Hyal3 overexpressed in cultured cells lacks intrinsic hyaluronidase activity and that Hyal3 may contribute to HA metabolism by augmenting the activity of Hyal1.
Key words: endoglycosidase / Hyal1 / Hyal3 / hyaluronan / hyaluronidase
2 These authors contributed equally to this work.