SMAD proteins are two protein families of intracellular signaling proteins that play a role in cell-cell communication. They are divided into two groups SMAD1 and SMAD2.
There is also a third group of family members, the SMAD3, which function as transcriptional regulators. They are involved in both signal transduction pathways and in gene transcription regulation.
Some common functions include inhibiting the expression of certain genes inside cells. Activating the expression of certain genes inside cells. Change the location, shape, or behavior (depending on function) of a cell.
To be more specific, the main function of the SMAD family is to transmit signals from transforming growth factor-beta (TGF-β). The TGF-beta signaling pathway is a network of molecular interactions that control cell growth and differentiation.
However, despite their crucial role in transducing TGF-β information, all SMADs are regulated by other TGF-β family members. SMAD proteins are highly specific to the type of TGF-β they recognize; for example, only SMAD1 and 2 can be activated by TGF-β1.
These proteins are part of a pathway that is essential for many developmental processes in mammals, such as embryonic patterning (formation of body structures), limb formation, heart development, and neural crest cell migration during head development.
One mechanism through which these proteins function is through regulating transcription of certain genes, such as Hox genes during development. The SMAD proteins have also been found to play a role in diseases, including cancer.
SMAD proteins control cell processes and behaviors without being affected by external stimuli. They can communicate over a large distance to control other cells or organs for the benefit of the organism as a whole. These proteins play an important role in many biological functions and their mechanisms are vital to the proper function of the human body.