Inside the cell, there exists a network of molecules. Between them, information is constantly being exchanged. ~ German microbiologist Ingo Schmitz
Every cell, whether a primordial yeast or post-modern human, has a complex high-speed system of pathways for transporting cargo within, such as proteins and various vesicles. Actin cables, formed into helical filaments, are protein-paved highways. Myosin molecules are nanoscale motor proteins that ply the filaments as transporters.
A cell’s transport network is highly optimized in paths and lengths: neither too long, nor coming up short. Every cell organically finesses a fiendishly difficult geometry problem. The problem is solved by feedback: passengers communicate to the cellular machinery providing the transport via protein tokens which regulate path growth.
Transport is just one facet of cellular communication. Intracellular chat transpires in numerous ways for a wide variety of functions related to every state and stage of a cell’s life.
Using peptides (protein fragments), status updates are regularly transmitted from deep within a cell to the cell’s surface, to keep the immune system and other interested parties informed about what is going on within the cell. (Peptide-loading complexes within the endoplasmic reticulum are responsible for production and quality control of messaging peptides.) At the cell surface, MHC-1 proteins filter the data in the status updates and present only relevant information to patrolling immune system cells.
(MHC-1 is a class of immune system related glycoproteins. MHC stands for major histocompatibility complex; a term referring to biological (tissue) compatibility. There are 3 MHC classes.)