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Lecture 7

DEV2011: Lecture 7 summary

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Monash University

LECTURE 7: Cell Signaling: Cell signaling occurs between cells of a single organism. However, cell signaling may also occur between cells of two different organisms. The ability of cells to perceive and correctly respond to their microenvironment is the basis of development, tissue repair, and immunity as well as normal tissue homeostasis. Contact-Dependent Signaling: It is a type of cell-cell or cell-extracellular matrix signaling in multicellular organisms that requires close contact. There are three types of contact- dependent signaling: - A membrane ligand (protein, oligosaccharide, lipid) and a membrane protein of two adjacent cells interact - A communicating junction links the intracellular compartments of two adjacent cells, allowing transit of relatively small molecules - An extracellular matrix glycoprotein and a membrane protein interact In cell-cell signaling, a cell places a specific ligand on the surface of its membrane, and subsequently another cell can bind it with an appropriate cell surface receptor or cell adhesion molecule. The notch signaling mechanism is an example of this, in which two adjacent cells must make physical contact in order to communicate. This requirement for direct contact allows for very precise control of cell differentiation during embryonic development. The extracellular matrix is composed of glycoproteins (proteins and glycosaminoglycan) produced by the organism's cells. They are secreted not only to build a supportive structure but also to provide critical information on the immediate environment to nearby cells. Indeed, the cells can themselves interact by contact with extracellular matrix molecules and as such, this can be considered an indirect cell / cell communication.Cells use mainly the receptor integrin to interact with ECM proteins. This signaling can influence the cell cycle and cellular differentiation. Endocrine Signaling: Many cell signals are carried by molecules that are released by one cell and move to make contact with another cell. Endocrine signals are called hormones. Hormones are produced by endocrine cells and they travel through the blood to reach all parts of the body. Specificity of signaling can be controlled if only some cells can respond to a particular hormone. Synaptic Signaling: Synaptic signaling is similar to paracrine signaling but there is a special structure called the synapse between the cell originating and the cell receiving the signal. Synaptic signaling only occurs between cells with the synapse; for example between a neuron and the muscle that is controlled by neural activity. Paracrine Signaling: Paracrine signaling is a form of cell-cell communication in which a cell produces a signal to induce changes in nearby cells, altering the behavior or differentiation of those cells. Signaling molecules known as paracrine factors diffuse over a relatively short distance (local distance), as opposed to endocrine factors (hormones which travel longer distances via the circulatory system), and juxtacrine interactions (autocrine signaling). Cells that produce paracrine factors secrete them into the immediate extracellular environment. Factors then travel to nearby cells in which the gradient of factor received determines the outcome. In order for paracrine factors to successfully induce a response in the receiving cell, that cell must have the appropriate receptors available on the cell membrane to receive the signals, also known as being competent. Additionally, the responding cell must also have the ability to be mechanistically induced. The highly conserved receptors and pathw
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