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Cystatin C in the Eye and in Specific Model Systems

Wasselius, Johan LU (2003)
Abstract (Swedish)
Popular Abstract in Swedish

Vår kropp består till stor del av proteiner. De bygger upp vår kropp, låter oss röra på armar och ben, se, höra, tänka och känna. Proteiner byggs av cellerna utifrån den individuella ritning - DNA - som vi alla bär med oss i cellernas innersta kärnor.



Lika livsviktigt som det är att kunna tillverka alla tusentals olika proteiner är det att kunna bryta ned dem i lagom takt. Det råder en delikat balans mellan uppbyggnad och nedbrytning av proteiner i kroppen och en rubbning av den balansen kan leda till svåra skador och sjukdomar. De proteiner som bryter ned andra proteiner kallar vi proteaser. Dessa proteaser kontrolleras av andra proteiner, som kan hindra deras nedbrytning och... (More)
Popular Abstract in Swedish

Vår kropp består till stor del av proteiner. De bygger upp vår kropp, låter oss röra på armar och ben, se, höra, tänka och känna. Proteiner byggs av cellerna utifrån den individuella ritning - DNA - som vi alla bär med oss i cellernas innersta kärnor.



Lika livsviktigt som det är att kunna tillverka alla tusentals olika proteiner är det att kunna bryta ned dem i lagom takt. Det råder en delikat balans mellan uppbyggnad och nedbrytning av proteiner i kroppen och en rubbning av den balansen kan leda till svåra skador och sjukdomar. De proteiner som bryter ned andra proteiner kallar vi proteaser. Dessa proteaser kontrolleras av andra proteiner, som kan hindra deras nedbrytning och därmed hindra att de gör skada. Dessa proteiner kallar vi proteashämmare.



I näthinnan, som utkläder baksidan av ögat, sitter de tappar och stavar som registrerar ljuset omkring oss och ger upphov till de nervsignaler som vi uppfattar som synintryck. Det är speciella proteiner i tapparna och stavarna som registrerar ljus och de behöver omsättas i en hög takt. En annan celltyp - näthinnans pigmentepitelceller - är specialiserad på just den uppgiften. Om nedbrytningen inte fungerar ansamlas stora mängder gamla proteiner från tapparna och stavarna vilket så småningom skadar näthinnan och gör oss blinda.



I den här avhandlingen visar vi hur cystatin C, en proteashämmare, uttrycks näthinnan och i andra delar av ögat. Vi visar i vilka celler det finns, och i vilka koncentrationer. Vi har också visat hur halten av cystatin C förändras i näthinnan under dess tidiga utveckling.



Vidare har vi undersökt var cathepsin B, ett proteas som kan hämmas av cystatin C, finns i olika delar av ögat, både i vilka vävnader det bildas och i vilka celler det finns, vilket visar sig vara väsentligen desamma som har cystatin C. Det verkar därmed troligt att cystatin C har som funktion att vid behov hämma cathepsin B i flera av ögats olika delar.



Slutligen har vi använt ett modellsystem bestående av makrofager, en typ av vita blodkroppar, för att visa att dessa kan ta upp cystatin C från sin omgivning. Det betyder att cystatin C även kan ha funktioner inuti cellerna.



Vi har också visat att celler i olika delar av ögat har förmågan att aktivt ta upp cystatin C från sin omgivning. De celler som tar upp cystatin C är generellt sett desamma som normalt innehåller cystatin C, vilket antyder att även detta cystatin C kan ha tagits upp av cellerna från sin omgivning. (Less)
Abstract
It is a necessity of life to make proteins, and it is an equal necessity to degrade those proteins, to eliminate dysfunctional proteins, and leave room for new ones. The processes of protein synthesis and degradation into peptides - proteolysis - have attracted a great interest during the last decades.



The eye contains several highly specialized tissues, in which the protein turnover is of vital interest. Reduced control of proteolysis might, for example, impair the transparency of the lens and the cornea. It may also reduce the capacity to eliminate used photoreceptor elements, a task normally carried out by the specialized retinal pigment epithelial cells, as part of the constant renewal and degradation of our... (More)
It is a necessity of life to make proteins, and it is an equal necessity to degrade those proteins, to eliminate dysfunctional proteins, and leave room for new ones. The processes of protein synthesis and degradation into peptides - proteolysis - have attracted a great interest during the last decades.



The eye contains several highly specialized tissues, in which the protein turnover is of vital interest. Reduced control of proteolysis might, for example, impair the transparency of the lens and the cornea. It may also reduce the capacity to eliminate used photoreceptor elements, a task normally carried out by the specialized retinal pigment epithelial cells, as part of the constant renewal and degradation of our photoreceptors, resulting in accumulation of debris, and leading to visual impairment.



We have identified cystatin C, on the mRNA and protein levels, in the mouse, rat and human eye. Furthermore, we have described its precise localization in the ocular tissues, using immunohistochemistry. We show that it is present in the epithelium, endothelium and the stromal cells of the cornea, the epithelial cells lining the ciliary processes, stromal cells of the iris, the lens epithelial cells, the pigment epithelial cells, ganglion cells and occasional other cells in the retina, as well as in the aqueous humor (paper I and II). Our mRNA data suggests that it is locally produced.



Cystatin C is the strongest of the few known inhibitors of the lysosomal cysteine protease cathepsin B. We have identified cathepsin B in ocular tissues, both on the protein and mRNA levels (paper III).



The immunoreactivity pattern of cathepsin B is strikingly similar to that of cystatin C in all examined ocular tissues apart from the retina, suggesting that cystatin C is a dominating cathepsin B inhibitor in vivo in the cornea, the ciliary body, the iris and the lens. In these cells, cystatin C appears to be localized to the cytoplasm, whereas cathepsin B is localized to the lysosomes. In the retina there are differences in staining pattern, suggesting that another cystatin may be the dominating inhibitor of cathepsin B activity.



Since cystatin C is a secreted protein, it is assumed to play its role in the extracellular compartment. There is no previously known specific uptake system for cystatin C. We show that there is an active, high-affinity, and energy-requiring uptake system for cystatin C into macrophages in vitro (paper IV), as well as into several cell types, in the cornea, the ciliary body and the retina, of the eye, in vivo as well as in vitro (paper V).



The cell types that take up cystatin C in the eye (paper V) are generally the same types that contain endogenous cystatin C (paper I and II), suggesting that much or all cystatin C seen intracellularly in the normal eye may have been taken up from the surrounding extracellular space. This uptake system may regulate the extracellular levels of cystatin C in the eye, and possibly also in other tissues. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Professor Theodorsson, Elvar, IBK/Neurochemistry, Linköping University
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Ophtalmology, protein uptake, ciliary body, lens, cornea, retina, eye, Cystatin C, cathepsin B, Oftalmologi
pages
150 pages
publisher
Johan Wasselius, WRC, BMC B13, Klinikgatan 26, 22184 Lund,
defense location
Rune Grubb salen, BMC, Lund
defense date
2003-12-12 10:15
ISBN
91-628-5793-2
language
English
LU publication?
yes
id
eff7b338-fa30-4ced-9eb5-fe7e9dc69a7e (old id 466335)
date added to LUP
2007-10-08 11:16:55
date last changed
2016-09-19 08:45:10
@phdthesis{eff7b338-fa30-4ced-9eb5-fe7e9dc69a7e,
  abstract     = {It is a necessity of life to make proteins, and it is an equal necessity to degrade those proteins, to eliminate dysfunctional proteins, and leave room for new ones. The processes of protein synthesis and degradation into peptides - proteolysis - have attracted a great interest during the last decades.<br/><br>
<br/><br>
The eye contains several highly specialized tissues, in which the protein turnover is of vital interest. Reduced control of proteolysis might, for example, impair the transparency of the lens and the cornea. It may also reduce the capacity to eliminate used photoreceptor elements, a task normally carried out by the specialized retinal pigment epithelial cells, as part of the constant renewal and degradation of our photoreceptors, resulting in accumulation of debris, and leading to visual impairment.<br/><br>
<br/><br>
We have identified cystatin C, on the mRNA and protein levels, in the mouse, rat and human eye. Furthermore, we have described its precise localization in the ocular tissues, using immunohistochemistry. We show that it is present in the epithelium, endothelium and the stromal cells of the cornea, the epithelial cells lining the ciliary processes, stromal cells of the iris, the lens epithelial cells, the pigment epithelial cells, ganglion cells and occasional other cells in the retina, as well as in the aqueous humor (paper I and II). Our mRNA data suggests that it is locally produced.<br/><br>
<br/><br>
Cystatin C is the strongest of the few known inhibitors of the lysosomal cysteine protease cathepsin B. We have identified cathepsin B in ocular tissues, both on the protein and mRNA levels (paper III).<br/><br>
<br/><br>
The immunoreactivity pattern of cathepsin B is strikingly similar to that of cystatin C in all examined ocular tissues apart from the retina, suggesting that cystatin C is a dominating cathepsin B inhibitor in vivo in the cornea, the ciliary body, the iris and the lens. In these cells, cystatin C appears to be localized to the cytoplasm, whereas cathepsin B is localized to the lysosomes. In the retina there are differences in staining pattern, suggesting that another cystatin may be the dominating inhibitor of cathepsin B activity.<br/><br>
<br/><br>
Since cystatin C is a secreted protein, it is assumed to play its role in the extracellular compartment. There is no previously known specific uptake system for cystatin C. We show that there is an active, high-affinity, and energy-requiring uptake system for cystatin C into macrophages in vitro (paper IV), as well as into several cell types, in the cornea, the ciliary body and the retina, of the eye, in vivo as well as in vitro (paper V).<br/><br>
<br/><br>
The cell types that take up cystatin C in the eye (paper V) are generally the same types that contain endogenous cystatin C (paper I and II), suggesting that much or all cystatin C seen intracellularly in the normal eye may have been taken up from the surrounding extracellular space. This uptake system may regulate the extracellular levels of cystatin C in the eye, and possibly also in other tissues.},
  author       = {Wasselius, Johan},
  isbn         = {91-628-5793-2},
  keyword      = {Ophtalmology,protein uptake,ciliary body,lens,cornea,retina,eye,Cystatin C,cathepsin B,Oftalmologi},
  language     = {eng},
  pages        = {150},
  publisher    = {Johan Wasselius, WRC, BMC B13, Klinikgatan 26, 22184 Lund,},
  school       = {Lund University},
  title        = {Cystatin C in the Eye and in Specific Model Systems},
  year         = {2003},
}