- Slides: 16
Cell Signaling Signal Transduction Pathways
Cellular Signaling • Autocrine Signals – Diffuse from one part of a cell to another part of the same cell • Synaptic signaling – Neurotransmitter is the signaling molecule – Occurs in the animal nervous system – Paracrine signals- send – messages to nearby cells by diffusion Endocrine signals, or hormones, travel anywhere in the blood to reach their target cells.
Signal Transduction Pathways • Coordinates the activities within, among, and between all individual cells, which supports the entire organism • Ligands – Chemical in low concentrations that reach target cells by local diffusion or via the circulatory system • Ligands bind to receptors – On cell membrane or inside the cytoplasm of the target cell • Examples include ion channel receptors, G-protein –coupled receptors, and protein kinase receptors • End product of the signal transduction pathway is a change in gene expression, a change in protein activity, or apoptosis (cellular death)
Secondary Messengers • Once the signal is transmitted from outside the cell to the cytoplasm, a secondary messenger propagates the signal • Most common example: c. AMP (cyclic AMP) – The ligand, or first messenger, is not able to enter the cell
The Cascade Effect • The multi-step cascade uses a small number of extracellular signal molecules to produce a major cellular response. • Amplifies the signal and provides numerous opportunities for cellular control, coordination, and regulation • Diversity of organisms with such similar pathways suggests that signal transduction pathways evolved from a common ancestor millions of years ago!!!
What do I NEED to know? • Signal transduction pathways … – Are Characterized by a signal, a transduction, and a response – Are Highly specific and regulated – One signal molecule can cause a cascade effect – Evolved millions of years ago in a common ancestor
Can you make the connections? • Imagine you just got a splinter! How does your body protect itself from the “foreign invader” and keep you healthy? Pause for discussion
The Human Immune System • We live in a world of germs! We must protect ourselves, so… • The three levels of the immune system are: – Nonspecific defenses, or barriers (innate) – Nonspecific defenses (inflammatory response) – Adaptive Immunity
First Line of Defenses • Non-specific to help prevent pathogens from entering • Like soldiers patrolling the area • • Skin Mucous Tears- lysozyme Stomach acid
Question to Ponder Can you think of a time in which you used any of these defenses? How do you think it worked?
Second Line of Defense • Non-specific • Inflammatory response – Histamines trigger vasodilation – Release of phagocytes and prostaglandins • White blood cells attack invaders • Prostaglandins increase blood flow – Chemokines are secreted • Attracts phagocytes to site
Third Line of Defense • Adaptive Immunity – B lymphocytes and T lymphocytes (both arise from stem cells) • Both recognize specific antigens – Specific responses • Recognition – B and T cells recognize specific antigens on APC (antigen presenting cells) • Activation phase – Rapid cell division – Makes effector and memory cells • The effect phase – B cells produce humoral response – T cells produce cell-mediated response
Interferons • Interferons are protein signals released by cells infected by viral pathogens • http: //www. dnaftb. org/35/animation. html
Question to Ponder • Discuss with your partner how adaptive immunity could utilize cell signaling pathways. • How is your second line of defense like a signal transduction pathway? – What parts of the inflammatory response are represented in the cell signaling pathway? Can you draws parallels between the parts of this response to the parts of a signaling pathway?
Are you ready… • Which of the following is directly responsible for humoral immunity? A. Cytotoxic T-cells B. Helper T-cells C. Macrophages D. B cells
Keep it up… • Of all the following, what part does not participate in nonspecific immune defense? A. Immunoglobulins B. Macrophages C. Skin D. Natural Killer Cells