What are protein interactions?
Much like the name implies, protein interactions are the dynamic ways in which proteins associate with each other in various tissue- and organism-dependent manner. While virtually no protein is able to act alone, the other proteins it interacts with give great insight into the function and cellular processes a particular protein is involved in.
Why do we study protein interactions?
Protein interactions are vital to the understanding of disease progression and pathogenesis. By understanding the way proteins interact in a normal, non-disease state, scientists and physicians can find disparities in the disease state. These disparities can then become targets for novel drug treatments and therapies in a more individualized fashion.
How do we study protein interactions?
Protein interactions can be studied in a variety of methods. Microbes and model organisms are often used because many protein networks are conserved throughout species. These interactions are detected by a variety of experimental methods, such as yeast two-hybrid and mass spectrometry. Yeast two-hybrid experiments are useful for assessing interactions within the nucleus, but have a high rate of false positives and negatives. Mass spectrometry comes in a variety of forms, each with its own advantages and disadvantages which should be assessed for each individual project. Databases are also a useful tool for protein interaction analysis, such as String, BioGrid, and IntAct. These, together with gene ontology, can provide a greater insight into the function, localization, and process the protein of interest is involved in and guide further experiments.
What does the FKBP5 protein interact with?
Above are the FKBP5 protein interactions present in humans, rats, fruit flies, and mice found in String. While many of them share interactions, such as with heat shock proteins (designated by "HSP" and numbers), there are many different interactions between them. This may be partially a result of incomplete identification of the extensive protein interaction networks, as we never truly know everything in science, or with subtle difference with protein homolog structure or the tissue sampled. It is also important to note that the FKBP5 protein is not confined to only depression pathogenesis, but is also found in prostate cancer through its interaction with AKT and mTOR and the androgen receptor.
 Ellsworth, Katarzyna Anna and Wang, Liewei. FKBP5 (FK506 binding Protein 5). (2013). Retrieved from http://atlasgeneticsoncology.org/Genes/FKBP5ID40578ch6p21.html