What is the primary purpose for the receptor proteins located within the cell

Receptor proteins are molecules inside a cell or on its surface on which ligands bind. A ligand is any substance (e.g. a hormone, drug, functional group) that binds specifically and reversibly to another chemical entity to form a large complex. Receptor proteins found inside a cell are called internal receptors or intracellular receptors or cytoplasmic receptors. They act as regulators of mRNA synthesis to mediate gene expression. When a ligand binds to an internal receptor, the receptor changes in conformation and exposes on itself a site that can bind to DNA. The receptor joined to the ligand moves into the nucleus where it binds to a specific site on the cell DNA. Once bound, it promotes the process of transcription where information is copied from DNA to mRNA

In my own word cell technology can  lead to advances in the understanding of diseases mechanism and transmission because diseases is very bad