PPT CELL SIGNALING

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Presentation Transcript

Cell Signaling : 

Cell Signaling Cell communication

Cell Signaling : 

Cells sense and send information (signals) Cells communicate with each other Cells must sense and respond to changes in the environment The signal can come from inside the cell, from another cell, or from the environment. Cell Signaling 2 BY NITIN SONAWANE RGPV BHOPAL

Generic Signaling Pathway : 

Generic Signaling Pathway Signal Receptor (sensor) outside Transduction Cascade cytosole Output Something happens 3 BY NITIN SONAWANE RGPV BHOPAL

Responses to cell signaling : 

Responses to cell signaling Gene expression is altered at the level of transcription, RNA processing or translation Enzyme activities are altered Protein-protein interactions are induced or inhibited The localization of certain proteins and other stuff is altered 4 BY NITIN SONAWANE RGPV BHOPAL

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The Cell… divides or stops dividing differentiates commits suicide or kills something moves somewhere or stops moving alters its metabolism passes on the signal 5 BY NITIN SONAWANE RGPV BHOPAL

What can be a signal? : 

What can be a signal? Peptides - insulin, glucagon... Proteins Amino acid derivatives - epinephrine, histamine Other small biomolecules - ATP Steroids, prostaglandins Gases - Nitric Oxide (NO) Photons Damaged DNA Odorants, tastants 6 BY NITIN SONAWANE RGPV BHOPAL

Types of Cell Signaling : 

Types of Cell Signaling 7 BY NITIN SONAWANE RGPV BHOPAL

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The same signal can produce different effects in different cells : 

The same signal can produce different effects in different cells 9 BY NITIN SONAWANE RGPV BHOPAL

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Types of Signals based on Where they Bind To an intracellular receptor: e.g. Steroid hormones To a cell-surface receptor: G-protein linked, enzyme-linked, or ion channel-linked 10 BY NITIN SONAWANE RGPV BHOPAL

Cell Signaling : 

Cell Signaling A. Ligand gated ion chanel B. Cell Surface Receptors: G-protein linked receptors Tyrosine kinase linked type Intra cellular steroidal type 11 BY NITIN SONAWANE RGPV BHOPAL

Cell Surface Receptors: G-protein linked receptors : 

Cell Surface Receptors: G-protein linked receptors Largest family of cell surface receptors Different ones respond to a wide variety of mediators including different hormones, neurotransmitters, local mediators Examples: Receptors to epinephrine, acetylcholine, serotonin 12 BY NITIN SONAWANE RGPV BHOPAL

Functions of Cell Surface Receptors : 

Functions of Cell Surface Receptors G proteins are guanine nucleotide-binding proteins that assist in transmitting signals to intracellular targets. G protein-coupled receptors are structurally and functionally related proteins characterized by seven membrane-spanning a helices. cAMP is an important second messenger that mediates cellular responses to a variety of hormones. 13 BY NITIN SONAWANE RGPV BHOPAL

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What do G-protein receptors do? G-protein receptors activate trimeric G-protein Activated G-protein alters the cellular concentration of a “second messenger”: usually cyclic AMP or Ca2+ The second messenger activates a protein kinase enzyme The protein kinase phosphorylates another enzyme and alters its activity BY NITIN SONAWANE RGPV BHOPAL 15

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Trimeric G-proteins disassemble when activated Three chains: a, b, and g a chain binds and hydrolyzes GTP b & g chains form a tight complex bg that anchors G-protein to the plasma membrane BY NITIN SONAWANE RGPV BHOPAL 16

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Trimeric G-proteins disassemble when activated Inactive G-protein has a bound GDP When activated: GDP dissociates, new GTP is bound This causes a to dissociate from bg a binds to adenylate cyclase, altering its activity Gs protein stimulates activates adenylate cyclase, Gi inhibits it BY NITIN SONAWANE RGPV BHOPAL 17

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Receptor Protein-Tyrosine Kinases : 

Receptor Protein-Tyrosine Kinases Receptor protein-tyrosine kinases phosphorylate their substrate proteins on tyrosine residues. The human genome encodes 59 receptor protein-tyrosine kinases, including the receptors for EGF, NGF, PDGF, insulin, and many other growth factors. 20 BY NITIN SONAWANE RGPV BHOPAL

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Intracellular Receptor Signaling: Steroid Hormones : 

Intracellular Receptor Signaling: Steroid Hormones Overview of Steroid Hormone Action: Steroid hormone (small, hydrophobic) is secreted by glandular cells and released into bloodstream (usually transported via shuttle proteins) The hormone enters the cytoplasm of cells In the cytoplasm of target cells, the hormone binds to steroid hormone receptor protein 23 BY NITIN SONAWANE RGPV BHOPAL

Intracellular Receptor Signaling: Steroid Hormones : 

Intracellular Receptor Signaling: Steroid Hormones Overview of Steroid . . . (cont.): The steroid-receptor conplex is translocated into the nucleus, where it activates the transcription of the primary response genes Transcription of the primary response genes, followed by translation, results in the production of primary response proteins 24 BY NITIN SONAWANE RGPV BHOPAL

Intracellular Receptor Signaling: Steroid Hormones : 

Intracellular Receptor Signaling: Steroid Hormones Overview of Steroid . . . (cont.): The primary response proteins usually inhibit further transcription of their own genes, and they may activate transcription of secondary response genes. 25 BY NITIN SONAWANE RGPV BHOPAL

Steroid Hormones and the Nuclear Receptor Superfamily : 

Steroid Hormones and the Nuclear Receptor Superfamily Hormones are signaling molecules that are produced by endocrine glands that act on cells at distant body sites. Steroid hormones are a group of hydrophobic hormones that are derivatives of cholesterol. Testosterone is a steroid hormone produced by the testis. 26 BY NITIN SONAWANE RGPV BHOPAL

Steroid Hormones and the Nuclear Receptor Superfamily : 

Steroid Hormones and the Nuclear Receptor Superfamily Estrogen and progesterone are steroid hormones produced by the gonads. Corticosteroids are steroid hormones produced by the adrenal gland. Glucocorticoids are steroids produced by the adrenal gland that act to stimulate production of glucose. Mineralocorticoids are steroid hormones produced by the adrenal gland that act on the kidney to regulate salt and water balance. Thyroid hormone is synthesized from tyrosine in the thyroid gland and it plays important roles in development and regulation of metabolism. Vitamin D3 regulates Ca2+ metabolism and bone growth. Retinoic acid is a signaling molecule synthesized from vitamin A. Retinoids play important roles in vertebrate development and are synthesized from vitamin A. The nuclear receptor superfamily is a family of transcription factors that includes the receptors for steroid hormones, thyroid hormone, retinoic acid, and vitamin D3. 27 BY NITIN SONAWANE RGPV BHOPAL

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THANK YOU : 

THANK YOU BY NITIN SONAWANE RGPV BHOPAL 29