9.3 Response to the Signal

9.3 Response to the Signal

  • Because they are components of the cell, they are easy to interact with.
    • Phosphatidylinositol plays a role in cellular signaling.
    • The PI-phosphate and the PI-bisphosphate are formed by thephosphorylation of the PI.
  • These products are used as second messengers.
    • serine and threonine are phosphorylates in the target proteins when diacylglycerol is present.
    • The signal cascade continues when IP3 diffuses into the cytoplasm and binding to calcium channels in the reticulum.
  • PIP2 is broken down into two messengers, the second of which is theidase C.
  • Inside the cell, ligands can affect the cell's genes and machinery.
    • A variety of effects on the cell can be produced using signal transduction pathways.
    • The results of signaling pathways can be very different depending on the type of cell involved as well as the external and internal conditions.
    • A small sample of responses is described.
  • The transcription ofRNA is regulated by signal transduction pathways.
    • They regulate the translation of genes.
  • The MAP kinase ERK regulates translation in the nucleus.
    • The MAPK/ERK pathway is a chain of proteins in the cell that communicate a signal from areceptor on the surface of the cell to the nuclear DNA.
    • When ERK enters the nucleus, it causes aphosphorylation of aprotein kinase that regulates the translation of genes.
  • ERK works when it is phosphorylated.
    • ERKphosphorylates eIF-4E, an initiation factor that is associated with mRNA.
    • When eIF-4E becomes phosphorylated, the nucleus can begin to synthesise.
  • One of the mechanisms of gene regulation involves the interaction of aProtein that acts as an inhibitor.
    • In this case, the Ik-B is aUbiquitin, which is bound to the regulatory NF-kB.
    • The complex cannot enter the nucleus of the cell if Ik-B is phosphorylated by PKC.
    • The process of transcription is activated by the effect of phosphorylation.
  • Muscle cells are affected by another signaling pathway.
    • Adrenaline is a hormone that is produced by the adrenal glands and is used for short-term emergencies.
    • Cyclic AMPphosphorylates two enzymes.
    • In order for the degradation of glycogen to occur, the first enzyme must be activated by the intermediate glycogen phosphorylase kinase.
    • Phosphorylation of the GS causes it to not be able to form glycogen from glucose.
    • In this way, a muscle cell can get a ready pool of glucose by using its own muscles to form it, and by blocking the use of glucose to form it, thus preventing a futile cycle of glycogen degradation and synthesis.
  • Cell signaling pathways are involved in cell division.
    • Cells don't divide unless they are stimulated by other cells.
    • Most growth factors bind to cell surface receptors.
    • RtKs are cell surface receptors.
    • The expression of genes that interact with other cellular components is stimulated by the MAP kinase.
  • Cancer biologists study the origins of cancer with the goal of developing new prevention methods and treatment strategies that won't harm the normal cells of the body.
    • Cell growth is controlled by signaling pathways.
    • The signaling pathways are controlled by signaling genes.
    • There are genes that can result in malfunctioning signaling.
    • Unrestricted cell division and possibly cancer can be caused by this.
    • One type of oncogene that has the potential to cause cancer is the genes that regulate the signaling.
    • The original discovery of the oncogene was made when it was linked to cancer.
    • 30 percent of cancer cells have a variation in the RAS gene that leads to uncontrollable growth, according to further studies.
    • If left unaddressed, cell division can lead to the growth of cancer cells in new locations in the body.
  • Cancer biologists have been able to identify many other oncogenes that contribute to the development of cancer.
    • In 20 percent of human breast cancers, HER2 is present in excessive amounts.
    • 25 percent of breast cancer patients have HER2 overexpression, which led to the development of a drug called Herceptin.
    • Herceptin targets HER2 in the immune system.
    • Herceptin therapy helps control signaling.
    • The use of Herceptin in combination with chemotherapy has helped increase the survival rate of patients with breast cancer.
  • The National Cancer Institute has more information on cancer biology research.
  • Apoptosis allows a cell to die in a controlled manner that prevents the release of potentially damaging molecule from inside the cell.
    • A cell can initiate the process of apoptosis if there are abnormality in the cell's health.
    • The cell's normal checks and balances can fail in some cases.
    • Apoptosis can also be initiated by external signaling.
    • The extracellular matrix is a network of glycoproteins that provides structural support for cells in an organisms.
    • There is a signaling cascade within the cell.
    • The signaling ceases if the cell moves away from the matrix.
    • The system keeps cells from moving through the body and out of control.
  • T-cell development is an example of external signaling that leads to apoptosis.
    • T-cells are immune cells that destroy foreign particles and macromolecules.
    • Normally, T-cells don't target their own "self" proteins, a process that can lead to autoimmune diseases.
    • In order to develop the ability to discriminate between self and non-self, immature T-cells undergo screening.
    • If the T-cell receptor is binding to self proteins, the cell will kill the potentially dangerous cell.
  • Normal embryological development is affected by apoptosis.
    • The formation of web-like tissue between individual fingers and toes is found in the early stages of development in animals.
    • These unneeded cells must be eliminated in order for fingers and toes to form.
    • The cells between the developing digits are destroyed by a cell signaling mechanism.