How do receptor proteins get into urine??

[bs07cp]

Hello

Im a bit embrassed to ask my professor/supervisor this question becuase it is probably very simple...

I am doing a research project based on identivying a binding antibody to the cell surface transmembrane protein known as 'FGFR3' which is being developed as a biomarker urine test for bladder cancer (urothelial cell carcinoma), due to overexpression and/ or mutational activation.

A question ive been asked my a professional is 'how would this protein get into the urine'??

Ive been thinkin about this question..and i am thinkin that it could get excised by membrane-associated proteases releasing the soluble extracelular domain into the extracelular space of epithelial bladder tissue....but wondering ow it would find its way in to the urine of the patient?? Any ideas...maybe glomerula filtration in the kidneys...

Thanks, callum

[canalon]

Dead epithelial cells peeling off the bladder membrane and being evacuated in the urine?My 2 cents.