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Intercellular
Medical Cell Biology
Term | Definition |
---|---|
Hydrophobic | Small, easily diffuse across membrane, activate receptors inside target cells (transcription factor), directly interact |
Hydrophilic | Large, cannot across membrane, use cell surface receptors to transmit signals within cells |
Types of receptors | Extracellular, transmembrane receptor, membrane receptor, intracellular receptor |
Membrane receptors/cell surface receptor | Ion channel (linked receptor), G-protein coupled receptors, enzyme-linked receptors |
G-protein coupled receptor | 7 TM proteins, activate trimeric G-protein (alpha, beta, gamma), Activated alpha-subunit will activate adenyl cyclase, which will increase cAMP, which will activate PKA, which will increase transcrpition |
Ion channel-linked receptor | cation and anion channels, involved rapid signalling-excitatory neurons, opening and closing of channels is controlled by Nt |
Enzyme linked receptor | enzyme binds to a receptor |
Steroid receptors are associate with the following: | Zinc finger and HRE (hormone response element) |
Muscurinic | when acetylcholine binds to an organ receptor |
The effects of acetylcholine binding to a salivary gland? | Saliva secretion |
The effects of acetylcholine on a heart biological receptor? | Decrease rate and force of contraction |
The effects of acetylcholine on a nicotinic receptor | Depolarization and contraction |
Short Distance Cell Signaling | Paracrine, autocrine, and juxtacrine |
Long distance Cell Signaling | Endocrine and synaptic |
Paracrine | chemicals are releases in extracellular environment, exerts effect on neighboring cells. Example: NEUROTRANSMITTER |
Autocrine | Effect on itself, cells that synthesize the ligands-release the signaling ligand, which then act on the same cell. Example: INTERLEUKIN |
Juxtacrine | Ligand not released from synthesizing cells, remain attach to the plasma membrane, interact with receptors on adjacent cells. Example: Epidermal growth factor |
Endocrine | Hormone-released into circulation. Example: Insulin or Glucagon |
Synaptic | Specialized form of paracrine, signals are transmitted along neuronal processes |
Hormones | Diverse activities, act over long distances, time scale is from min-years, endocrine glands (pituitary, thyroid, pancreas, etc.), enter circulation-induce many changes in the cells |
2 Groups of hormones | 1. Lipophilic (hydrophobic)-steroid hormones 2. hydrophillic |
Lipophilic hormone | Easily pass through membrane, synthesized from cholesterol, do not store hormones, time is from hours to days, has nuclear receptors. Examples: sex hormones, corticosteroids, iodothyroxines (thyroid hormones). |
Retinoids | Synthesized from VITAMIN A and not from CHOLESTEROL |
Hormone signaling pathway | Hormone diffuse through plasma membrane, bind to nuclear receptor, forms a hormone/receptor complex, complex binds to HRE at the promoter region of DNA, gene transcription |
Glucocorticoid receptors | Receptor located in cytosol and is bound to HSP 70/90 (inactive), when receptor ligand complex is formed, HSP 70/90 is displaced, the whole complex translocates to the nucleus, dimer activates gene transcription |
Estrogen receptor signaling pathway | In nucleus inactive when bound to Hsp 90, when estrogen bound to receptor-displays Hsp90, activated receptor with estrogen-form a dimer, the dimer then bind to DNA w/HAT associated |
Thyroid Receptors | Receptor binds to DNA with or without presence of ligand. Absence of ligand--receptor is bound to HDAC. Presence of ligand -- receptor is bound to HAT |
Hydrophilic Peptide | Release hormone into the blood, bind to surface receptor, generates 2nd messenge, (IP3/cAMP), immediate action but only last a short time b/c hormones are quickly degraded. |
3 Classes | GPCR, Ligand-gated ion channel, catalytic receptors (insulin-tyrosine kinase receptor) |
Somatotropes | Secrete growth hr |
Lactotropes | Secretes prolactin |
Corticotrophs | Secrete adrenocorticotropic hormone (ACTH) |
Thyrotropes | Secrete thyroid-stimulating hormone (TSH) |
Gonadotrophs | Secrete follicle-stimulating hormone FSH and luteinizing hormone (LH) |
Classical Pituitary | somatotropes, lactotropes, corticotrophs, thyrotropes, gonadotrophs |
Non-classical hormone of pituitary | Growth factor, cytokines, neurotransmitter |
Growth factors | Mitogen, trophic factors, survival factors |
Mitogen | cell proliferation |
Trophic factors | promote growth |
survival factors | inhibit apoptosis |
NGF | down regulate = apoptosis, upregulate = survival |
EGF | epidermal growth factor, cell proliferation |
TGF-alpha | high concentration, stimulate growth, low concentration-inhibit growth |
PDGF | platelet derived growth factor, tissue repair |
VEGF | Vascular endothelial growth factor, increase vascular permeability |
Interleukin | proliferation and differentiation of the T and B lymphocytes |
Inhibins | Inhibits FSH secretion |
Activin | Regulate formation of early embryonic nervous system |
Interferons | Antiviral effects |
TNF | Tumor necrosis factor, suppression of tumor |
Insulin like GF | mitogens, tropic, survival factors |