Changes in Signal Transduction Pathways (College Board AP Biology)

• The majority of signal transduction factors are proteins
• As such, they are coded for by genes within the organism's genome
• All parts of the genome are susceptible to mutation
• This can cause a dramatic effect on the production of the transduction factor in question
• Absence of a correctly-formed transduction factor can cause failure of the signal transduction pathway

• A well documented example is the protein hormone insulin
  • A mutation in its gene can lead to ineffective insulin being expressed
  • This would lead to diabetes at an early (neonatal) stage of life
• Many insecticides used in agriculture affect signal transduction by activating neural pathways in insects, leading to hyperactivity and death
• Signal transduction inhibitors are one research route for cancer treatment, as many cancers are caused by signal transduction malfunctions

Consequences of Mutation on Transduction Proteins Diagram

Mutations can have a detrimental effect on the proteins necessary for signal transduction

• Signal transduction pathways can also be affected by chemical interference
• This can be by activating the pathway or by inhibiting part of it
• Examples include:
  • Lead poisoning; lead affects the nervous system and can lead to impairments in learning, memory and cognitive function
  • Ethanol has psychoactive effects that are caused by changes in the signal transduction proteins that in turn, cause changes in the excitability of certain neurons 
  • Polychlorinated biphenyls (PCBs), a group of industrial chemicals which have been banned in many countries for decades, have harmful effects on signal transduction pathways
• Enzyme inhibitors can block the effects of enzymes in a metabolic pathway, and in doing so, affect signal transduction pathways
• Denatured proteins can also affect pathways, such as when a ligand might not be recognized by an enzyme that has had its active site altered by denaturation