Design an experiment to follow a protein

Proteins that are destined outside the cell move from the endoplasmic reticulum to the Golgi apparatus, and from there outside the cell via vesicles. Secretory proteins, mostly glycoproteins, are moved across the endoplasmic reticulum membrane. Proteins that are transported by the endoplasmic reticulum and from there throughout the cell are marked with an address tag called a signal sequence. The N-terminus (one end) of a polypeptide chain (i.e., a protein) contains a few amino acids that work as an address tag, which are removed when the polypeptide reaches its destination. Proteins that are destined for places outside the ER are packed into transport vesicles and moved along the cytoskeleton toward their destination.

The majority of ER resident proteins are retained in the ER through a retention motif. This motif is composed of four amino acids at the end of the protein sequence. The most common retention sequence is KDEL (lys-asp-glu-leu). However, variation on KDEL does occur and other sequences can also give rise to ER retention. It is not known whether such variation can lead to sub-ER localizations.

So, as a cell biologist, you could disrupt these signals and see where the protein would end up.