Earlier studies identified
serglycin proteoglycan and its
heparin chains to be important for storage and activity of mast cell
proteases. However, the importance of
serglycin for secretion and activity of mast cell
proteases in response to
parasite infection has been poorly investigated. To address this issue, we studied the effects on mast cell
proteases in
serglycin-deficient and wild type mice after peritoneal
infection with the obligate intracellular parasite Toxoplasma gondii. In line with previous results, we found severely reduced levels of cell-bound mast cell
proteases in both noninfected and infected
serglycin-deficient mice. However,
serglycin-deficient mice secreted mast cell
proteases at wild type levels at the site of
infection, and enzymatic activities associated with mast cell
proteases were equally up-regulated in wild type and
serglycin-deficient mice 48 h after
infection. In both wild type and
serglycin-deficient mice,
parasite infection resulted in highly increased extracellular levels of
glycosaminoglycans, including
hyaluronan and
chondroitin sulfate A, suggesting a role of these substances in the general defense mechanism. In contrast,
heparan sulfate/
heparin was almost undetectable in
serglycin-deficient mice, and in wild type mice, it was mainly confined to the cellular fraction and was not increased upon
infection. Furthermore, the
heparan sulfate/
heparin population was less sulfated in
serglycin-deficient than in wild type mice indicative for the absence of
heparin, which supports that
heparin production is dependent on the
serglycin core
protein. Together, our results suggest that
serglycin proteoglycan is dispensable for normal secretion and activity of mast cell
proteases in response to peritoneal
infection with T. gondii.