【問題】關於狂牛症和普恩蛋白

[benh666 10]

最近似乎在台灣不管是民間或是政壇,吵得最兇的就是美國牛進口.

當然啦,prion在致病機制裏頭的角色雖然已經被證實

但還有許多的問題,像是如何感染正常的PrPc,如何通過血腦障壁等等

但我想問的是prion還沒進到人體之前的事

prion是一個misfolding protein 對於正常的PrPc來講

而且它會感染PrPc使之變為擁有beta-sheet結構的PrPsc

最後就會沉澱~

可是不管如何它終究還是個蛋白質,我們人把它給吃下去,經過胃的pepsin水解,再經過小腸中酵素的水解應該已經變成胺基酸了! 縱使它不能夠被分解,小腸也無法吸收比胺基酸還大的分子吧! 那prion是如何進到人體的呢??

希望回答時可以附上資料來源 謝謝:E

[benh666 10]

嗯嗯 不好意思我已經找到一些資料了

那我就自己回答自己的問題吧xd

我是從PudMed裡找到的paper

The pathogenesis of variant Creutzfeldt-Jakob disease (vCJD) is most likely to be dependent on intestinal entry of orally ingested infectious prion proteins, though tonsils or other oral portals of entry are possible. The exact route of entry of infectious prion proteins is uncertain but receptors for prion proteins such as laminin receptor precursor (LRP) may be expressed on intestinal brush border. Cellular prion protein (PrP©) is expressed on intestinal enteric nervous system and is separated by a single layer of epithelial cells from ingested infectious prion proteins. Intestinal M cells in the Peyer's patches may also transcytose prion proteins which may be transported to the lymphatic system by migrating dendritic cells underlying the M cells. The relative importance of the several potential portals of intestinal entry of infectious prion proteins is uncertain but may determine susceptibility of the population and also potential preventive strategies.

另一篇是一個總整理

The initial step, when prion protein transmigrates from the

gut and into the lymphoid system, has been proposed to

involve epithelial M cells, because these represent key sites of

enteric antigen sampling by facilitating the entry and delivery

of enteric pathogens into underlying lymphoid tissues via the

process of transepithelial transport (32). An experiment in

which artificial M cells, derived from carefully differentiated

intestinal-like cells, were required for transepithelial prion

transport in vitro indicated a role for M cells in prion

absorption (33). However, there has been little additional

research to further support this hypothesis, and the requirement

for M cells in prion transport has yet to be documented

using in vivo models.

基本上prion透過M-cell進入人體

而M-cell 在維基百科的解釋是這樣的

M cells (or microfold cells) are cells found in the follicle-associated epithelium of the

Peyer's patch. They transport organisms and particles from the gut lumen to immune

cells across the epithelial barrier, and thus are important in stimulating mucosal immunity.

Unlike their neigbouring cells, they have the unique ability to take up antigen from the lumen of the small intestine via endocytosis or phagocytosis

這真是讓我大開眼界!!! 竟然小腸可以直接用包吞作用把物質送進體內!!!

當然啦,prion是否也是經過此道程序還處於假設狀態,只有在in vitro中被證實

但in vivo是否如此未可知:o

上面兩篇paper節錄請原諒我沒有翻成中文

因為今天太疲倦了|-)

若有人想在下面po翻譯,我會很感激的:E