What are signal transduction mechanisms?

Most of the functions that the cells in our body undertake are the result of signals (mostly chemical) that come from various parts of the body.  These signals are telling our cells when to undertake some basic functions as when to divide, when to mature, when to start functioning, when to migrate to a different place and when to die.  These signals come from distant cells (known as endocrine signals, like hormones and growth factors); they come from neighboring cells (known as paracrine signals); they even come from within the same cell (known as autocrine signals).

To convert those signals into action by the cell requires a series of chemical reactions within the cell. It is a bit like a baton being passed in a relay race, with the message finally reaching the nucleus of the cell where certain target genes are switched on, leading the cell to perform the intended function.  The way the signal is processed within the cell (the 'chemical relay race') is known as signal transduction.  There are probably many hundreds of different signal transduction mechanisms in our cells to operate the myriad of functions going on at any one time.

The relationship between signal transduction and disease

Other than infectious diseases, most human diseases involve abnormal behaviour of cells and this is the direct result of abnormal signal transduction signalling either because the cell is being bombarded with an abnormal strength of signal or because the mechanisms within the cell have malfunctioned (as with cancer).  The incessant growth of cancer cells (in any form of cancer), the blockage of arteries (in atherosclerosis), the structural changes in the lining of the joint (in rheumatoid arthritis), the structural changes in the bowel wall (in ulcerative colitis and Crohn's Disease) are all due to abnormal signal transduction mechanisms.

Treating the problem

Many of the drugs that we use today work by altering signal transduction mechanisms.  With very few exceptions this is by accident. By that, we mean that drugs have been discovered in the first place because they were beneficial, and then only later were found to be working because they modified some signal transduction process that was behaving abnormally.  However, the problem with almost every drug is that in the process of correcting the abnormal function, they also do harm to other mechanisms in the body that are behaving normally.T  he trend in drug development now is to design drugs that are made purposefully to home in on particular signal transduction mechanisms.  The rationale is that by being specific in its action, the drug is more likely to work and less likely to do harm.  The problem with this approach is that most diseases are due to malfunction of a number of different signal transduction mechanisms.  Heart disease, for example, probably involves abnormalities of dozens of different signals.  Designing therapies that encompass this range of abnormalities is a major problem.