User:Fdemsas/p11 project rough draft

History:

The discovery of the p11 protein is accredited to Dr. Paul Greengard. He attended Hamilton College  in 1944 and graduated in 1948 with a bachelor's degree in Physics and Mathematics. He fostered his interest in biophysics and studied pharmacology at John's Hopkins University, in Baltimore, Maryland. He received his Ph.D. in Neurophysiology  from Johns Hopkins University. Inspired by scientist Alan Hodgkin, Greengard began work on the molecular and cellular function of neurons receiving his PhD in 1953. He continued his postdoctoral work at the University of London,  Cambridge University , and the  University of Amsterdam. Dr. Greengard is a member of the Board of Scientific Governors at The Scripps Research Institute. The acting chairman of the Fisher Center for Alzheimer's Research Foundation and serves on the board of the Michael Stern Parkinson's Research Foundation. Both foundations support the research Greengard conducts in his Laboratory at The Rockefeller University .Paul Greengard is a Nobel Laureate. In 2000 he was awarded the Nobel Prize in Physiology or Medicine  for his discovery of how  dopamine  and a number of other transmitters in the brain exert their action in the nervous system.

Experiment

Paul Greengard of Rockefeller University in New York and his colleagues conducted a series of experiments that resulted in the discovery of the p11 protein. Research was funded by the National Institutes of Health's National Institute of Mental Health (NIMH.

Greengard and his team of researchers conducted tests to explore how 5-HT1B  (5-hydroxytrptamine), the  serotonin  1B receptor, functions and also what proteins these receptors interact with in brain cells. Their findings concluded that 5-HT1B interacts with p11, more specifically p11 increases localization of 5-HT1B receptors at the cell surface. p11 is increased in rodent brains by antidepressants or electroconvulsive therapy. In an animal model of depression and in the brain tissue from depressed patients, p11 is decreased. Overexpression of p11 increases 5-HT1B receptor function in cells and recapitulates certain behaviors seen after antidepressant treatment in mice. There is a specificity in the interaction between p11 and 5-HT1B. Greengard discovered this after conducting a year two-hybrid screen using twenty six out of 29 double-positive prey clones containing the gene encoding p11. From this the found that p11 interacted with 5-HT1B receptors but not with 5-HT1A, 5-HT2A, 5-HT5A, 5-HT6, dopamine  D1 or D2 receptors, two irrelevant baits (C{Delta}115 and pRP21), or the empty plasmid. . The specific interaction has been verified in three other ways: In HeLa cells and brain tissue p11 was found to coimmunoprecipitate with 5-HT1B receptors; Immunofluorescence  studies show colocalization between p11 and 5-HT1B receptors at the cell surface; and finally distribution of p11  mRNA  in the brain resembles that of 5-HT1B receptor mRNA. Figure below shows these findings respectively.



The p11 protein helps regulate signaling of the brain messenger chemical serotonin, one of the key targets of  antidepressants  which has been implicated in psychiatric illnesses such as  depression. The interaction between serotonin 1b recebtor 5HT1B and p11 can be summarized as such: when p11 levels increases, the number of 5-HT1B receptors on the cell surface increase proportionately. Increased number of 5-HT1B receptors on the surface of the neuron increase the effectiveness of serotonin communication across the synapse. On the other had, when p11 levels decrease, fewer 5-HT1B receptors migrate from inside the neuron to the cell membrane at the synaptic clef, thus lowering the efficiency with which serotonin signaling can occur across the synapse.

p11 levels are directly involved in the development of depression, anxiety and similar psychiatric illnesses thought to involve faulty serotonin receptors. Greengard and his colleagues verified this by examining the p11 levels in the brains of depressed humans and "helpless" mice in comparison to non-depressed humans and control mice. Mice deficient in the p11 protein displayed depression-like behaviors while those with sufficient amount of p11 protein behave as if they have been treated with antidepressants. . Furthermore, levels of p11 were found to be substantially lower in depressed humans and helpless mice, which suggested that altered p11 levels are may be involved in the development of depression-like symptoms.

The researchers also administered two types of antidepressants- a tricyclic and monoamine oxcidase inhibitor-and electroconvulsive therapy (ECT) to the mice. They did so to determine the effect such treatments used to improve weak serotonin systems have on p11 levels in brain cells. It is important to note that these three antidepressants work in completely different ways. The results showed that treating depression in these three ways caused an increase in the amount of p11 in the brain of these mice- the same biochemical change. Greengard concludes: "So, it's pretty convincing that p11 is associated with the main therapeutic action of antidepressant drugs"

The levels of the p11 protein in humans and mice with symptoms of depression were substantially lower in comparison to the levels of p11 in non-depressed animals, Greengard and his colleagues hypothesized that increasing p11 levels would result in the mice exhibiting antidepressant-like behaviors, and the opposite if p11 were reduced. They used a test that is used to measure antidepressant-like activity to affirm this hypothesis. There findings were over-expressed p11 genes, compared to the control mice, had increased mobility and more 5-HT1B receptors at the cell surface capable of more serotonin transmission. When researchers molecularly removed or "knocked out" the p11 gene in mice, the found that the knockout mice had fewer receptors at the cell surface, less serotonin signaling, reduced responsiveness to sweet reward, and less mobile behaviors all characteristic of depression-like behaviors. The 5-HT1B receptors were also less responsive to serotonin and antidepressant drugs.

The opposite occurred when researchers molecularly knocked out the p11 gene in mice. Compared to control mice, knockout mice had fewer receptors at the cell surface, reduced serotonin signaling, decreased responsiveness to sweet reward, and were less mobile, behaviors which are considered depression-like. Also, the 5-HT1B receptors of p11 knockout mice were less responsive to serotonin and antidepressant drugs compared to those of control mice, which further implicates p11 in the main action of antidepressant medications. Antidepressant manipulations increase the p11 levels while depressant manipulations reduce it, therefore antidepressant medications should focus on the main action of the p11 proteins and increase levels of the protein in order to achieve and anti-depression effect.