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Microscopic techniques approach in studying protease<br />
inhibitor cystatin in immune cells<br />
Tina Zava{nik-Bergant 1 , Martina Bergant 2 , Ur{ka Repnik 1 , Gareth<br />
Griffiths 3 , Rok Romih 4 , Matja` Jeras 2 , Janko Kos 5 , and Vito Turk 1<br />
1<br />
Department of Biochemistry and Molecular Biology, Jo`ef Stefan Institute, Ljubljana,<br />
Slovenia; 2 Tissue Typing Center, Blood Transfusion Center of Slovenia, Ljubljana, Slovenia;<br />
3<br />
European Molecular Biology Laboratory (EMBL), Heidelberg, Germany; 4 Institute of Cell<br />
Biology, Medical Faculty, University of Ljubljana, Slovenia; 5 Faculty of Pharmacy, University<br />
of Ljubljana, Slovenia<br />
Dendritic cells possess a big capacity to elicit immune response. Their maturation<br />
occurs as they migrate from peripheral tissues to lymphoid organs, where they present<br />
captured antigens to T cells. The central role of endosomal/lysosomal proteolytic<br />
enzymes in generating antigenic peptides and controlling MHC II traffic defines<br />
these enzymes as an important area of investigation. The involvement of natural<br />
protease inhibitors has been supported by the study on the cystatin homologue,<br />
secreted from filiar parasite, which was shown to down-modulate MHC II-restricted<br />
antigen presentation. Our study has been predominantly focused on human cystatin<br />
C expressed in dendritic cells in response to their differentiation and activation<br />
Dendritic cells are represented as a cell model in which a combination of confocal<br />
microscopy and quantitative electron microscopy was successfully applied in order to<br />
study endogenous and added cystatin C.<br />
We have shown that in immature dendritic cells cystatin C content was highly elevated<br />
compared to their precursors. The low content of cystatin C in monocytes resulted from<br />
lower expression, but not from its elevated secretion. Increased expression of cystatin<br />
C<br />
36l21<br />
and high content in Golgi apparatus were observed in immature dendritic cells. The<br />
transport of cystatin C was shown from Golgi apparatus towards the cell membrane,<br />
where cystatin C accumulated in fully mature dendritic cells. Differentiation and<br />
maturation dependence of endogenous cystatin C supports its intracellular regulatory<br />
potential and further suggests it new role in Golgi apparatus of immature dendritic cells.