Below is a figure showing an experiment where researchers measured total collage

Question

Below is a figure showing an experiment where researchers measured total collagen in cells (lysate) verses Collagen that was secreted from the cells (medium). These levels were measured in un-modified cells (control) or in cells where the protein sLY1 was knocked down by RNAi (SLY1) or where Tango1 was knocked down by RNAi (TANG01). The amounts from B were measured and expressed as a ratio of external internal in C. Based on this figure what role do you think SLY1 and TANG01 play in the cell? Why is it important for them to measure the amount of Collagen in the lysate? What is the Tubulin a control for?

Explanation / Answer

A. Collagen secreted into extracellular space and turns into extracellular matrix for cell attachment, tissue organization etc. Collagen produced inside the cells are folded in ER. TANGO1 binds to collagen and delays the release of collagen from ER so vesicle or bulky cargo pack a collagen in it. SLY1 fuse the membrane involve in protein trafficking in ER, Golgi complex and Vesicles this helps cargo pass from one compartment to another compartment.

So both the proteins needed to transport the collagen from inside the cells to other membrane.RNAi inhibits both the process of TANGO1 and SLY1 so collagen can't able to secrete in the medium, all the collagen arrested inside the cells itself it clearly shows in the picture.

B. We need to know the collagen is truley secreted inside the cells or not. If there is no secretion of collagen inside the cells lysate then the medium also shows no collagen. To confirm that the collagen present inside the cells but the two proteins TANGO1 and SLY1 responsible for movement of collagen from inside the cells to outside membrane.

Tublin independent to this collagen secretion and packaging. It always present in cells during mitosis and in cytoskelton.

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