Receptor-mediated uptake in vivo

[N.P.Dantuma at biol.ruu.nl]

In article <imnr.49.000BB0F9 at connectnet.com> imnr at connectnet.com (Immune Response) writes:
>From: imnr at connectnet.com (Immune Response)
>Subject: Receptor-mediated uptake in vivo
>Date: Thu, 7 Dec 1995 11:41:23

>Hello all!

>Does anyone have any ideas other than competition to prove receptor-mediated 
>uptake of a protein?

>Jose E. N. Gonzales

Hi Jose,

I don't know if you can use the following methods in vivo but they sure work 
in vitro. Receptor-mediated endocyotsis requires in general clathrin. Thus, 
inhibiting endocytosis by inhibiting clathrin is a strong indication for 
receptor-mediated endocytosis. Clathrin can be inhibited by, for example, 
acidification of cytosolic pH (by NH4Cl) or K depletion.
One of the last issues of Current Opinion in Cell Biology contains several 
reviews dealing with intracellular trafficking, including different 
endocytotic mechanisms. I think this may give you some clues.
Proving saturablity of endocytosis by incubating with an excess of unlabeled 
ligand and monitoring internalization and/or degradation of labeled ligand,
as you imply in your question, is even better than demonstrating 
involvement of clathrin. So what is wrong with that method?
If you need references, let me know by e-mail.

Nico Dantuma
Utrecht University
The Netherlands 
e-mail: N.P.Dantuma at biol.ruu.nl