How regulated protein translocation can produce switch-like responses.
It is widely appreciated that the regulated translocation of signaling proteins can increase the specificity and speed of signal transduction. It is less obvious that regulated translocation can also, in principle, turn a graded response into a more switch-like one. For example, if two or more signaling proteins are induced to translocate, the result can be a switch-like, ultrasensitive response. A switch-like response will also occur if translocation raises the local concentration of a signaling protein sufficiently to partially saturate the enzyme that inactivates it. These mechanisms are likely to make the mitotic activation of CDC2 (which is accompanied by the nuclear translocation of both CDC2-cyclin-B1 and its activator, CDC25C) and the growth-factor-induced activation of MAP kinase (which, upon sustained activation, concentrates in the nucleus and might thereby partially saturate the relevant MAP-kinase phosphatases) more switch-like.
Ferrell
J E
JE
Dept of Molecular Pharmacology, Stanford University School of Medicine, CA 94305-5332, USA. ferrell@cmgm.stanford.edu
D001692:Biological Transport; D016203:CDC2 Protein Kinase / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D008938:Mitosis; D008954:Models, Biological; D010766:Phosphorylation; D011506:Proteins / Q000378:metabolism*; D015398:Signal Transduction; D020687:cdc25 Phosphatases
D018797:Cell Cycle Proteins; D019926:Cyclin B; D056744:Cyclin B1; D011506:Proteins; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D016203:CDC2 Protein Kinase; D020687:cdc25 Phosphatases