Chapter 9 - Cell Communication Flashcards by Elie Zgheib

What does effective signaling require?

Ligand and Receptor Protein

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Signaling molecule (amino acid, peptide, large protein, individual nucleotides, steroids, lipids, dissolved gases such as Nitrous Oxide NO)?

Ligand

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Molecule to which signal binds?

Receptor Protein

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Where are receptor proteins located?

On plasma membrane or within a cell

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Complex made of ligand and receptor protein

Complex ligand-receptor

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what is signal transduction

signal that results in a cellular response

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How does signal response work

Cell responds to only one signal and ignores the rest depending on kind and number of receptors

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What is the general process of signal transduction

Ligand binds to receptor with complementary shape, induced change of receptor shape, initiation of signal transduction pathway, cellular response

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What are the basic mechanisms of Cellular Communication

1- Direct Contact
2- Paracrine Signaling
3- Endocrine Signaling
4- Synaptic Signaling

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What is direct contact

cells are close to each other & molecules on surface of cells are recognized by receptors of adjacent cell.

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Examples of direct contact

Embryonic development
Gap Junction

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What is Paracrine Signaling

signal molecules diffuse through extra-cellular fluid to nearby cells & only affects nearby cells

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Characteristics of signals in Paracrine Signaling

Short-lived & Local Effect

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Examples of Paracrine Signaling

early development, immune cells, and growth factors

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What is endocrine signaling

signal molecules enter the circulatory system and travel through the body

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Where do secretions of endocrines go

Travel to distant cells

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Characteristics of signals in Endocrine Signaling

long-lived & distant effect

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Examples of Endocrine Signaling

Hormones

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What are the signal molecules in synaptic signaling

Neurotransmitters released by nerve cells

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What is synaptic signaling

Neurotransmitters travel from tip of nerve cells to nearby target cells through a synaptic gap

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What is a chemical synapse

Neuron & Target cell

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Characteristics of signal in synaptic signaling

Short-lived & brief effect

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examples of synaptic signaling

acetylcholine, glutamate, and GABA

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what is autocrine signaling

cells secrete signals that bind to specific receptors on their own plasma membrane
they respond express and respond to secreted signals

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examples of autocrine signaling

signaling in immune system

what are signal transduction pathways

complex and discrete pathways

what is signal transduction

events that occur on receipt of a signal

what is the path for signal transduction

Ligand binds to receptor protein, forms complex, response

what is protein phosphorylation

control of protein function

what does protein kinases do

add phosphate from ATP to a protein

what is dephosphorylation

removal of a phosphate group from a protein

relation of phosphorylation and dephosphorylation to a protein

protein is activated by phosphorylation. deactivated by phosphorylation *reverse works*

how are receptors defined

by location and specific ligand binding

Characteristics of intracellular receptors

In cytoplasm and bind to hydrophobic ligands inside the cell

Characteristics of membrane receptors

transmembrane protein in plasma membrane, cytoplasmic or extracellular domain, bind to hydrophobic ligands outside the cell

Characteristics of Cell surface receptors

transmembrane protein in plasma membrane, cytoplasmic or extracellular domain, bind to hydrophobic ligands outside the cell

Types of Cell surface/membrane receptors

Channel-linked, enzymatic, and G-protein coupled receptors

characteristics of channel-linked receptors

Chemically/ligand gated ion channel, no energy needed, moves down concentration gradient

characteristics of enzymatic receptors

integral mb proteins, act or linked to enzyme, catalytic rxn on cytoplasmic portion, protein kinases

characteristics of G-protein coupled receptors

integral mb proteins, linked to G-protein

what causes G-protein conformation change

ligand binding

characteristics of steroid hormones

small, non-polar, bind to steroid hormone receptor, pass through plasma mb

function of steroid hormone

regulation of gene expression, production of proteins

functional domains of steroid receptors

hormone-binding, DNA-binding, interacts with coactivators to affect gene expression

inactive state of steroid receptor

inhibitor protein occupies DNA binding sight

hormone activation of steroid receptor

signals bind, change of receptor, inhibitor release, exposed DNA binding sight, receptor activation

gene expression activation of steroid receptor

receptor binds to DNA nucleotide seq in the nucleus, cell response is change I gene expression

how do coactivators work

intracellular responses act in concert with coactivators

difference in cell responses to the same signal is due to

number + nature of coactivators

how does the estrogen hormone affect the mammary tissue

coactivator is lacking, hormone interacts with another protein, gene expression decreases

how does the estrogen hormone affect the uterine tissue

presence of coactivator, complex estrogen-receptor binds to coactivator, gene expression increases (prepare uterus for pregnancy)

what is the receptor for NO gas

Guanylyl cyclase complex

how does Guanylyl cyclase complex work

NO binds to it, activating it, then catalyzes the synthesis of cGMP

what is the receptor for viagra

Sildenafil - cGMP phosphodiesterase complex

what is a protein kinase

enzymatic receptors that alter protein function by phosphorylation

what is an RTK

Receptor Tyrosine Kinases

Function of RTK

recognize hydrophilic ligands

Signaling via RTK influences what processes

cell cycle cell migration cell metabolism cell proliferation stimulate cell division

Mutations in RTK or Alterations of RTK signaling pathways can cause

cancer

Continuous signaling from RTK causes

Continuous cell proliferation

what is a plant receptor kinases

serine-threonine kinases

structure of RTK

single transmembrane domain, extracellular ligand-binding domain, intracellular kinase domain (catalytic site)

what does the catalytic site do

acts as a protein kinase that phosphorylates tyrosine

what occurs upon ligand binding

Dimerization & autophosphorylation

what is Dimerization

2 receptor-ligand complexes associate together

what is autophosphorylation

2 receptor-ligand complexes phosphorylate eachother

what does activation of the tyrosine kinase domain do

phosphorylation of intracellular targets (response proteins)

what does an activated receptor do

add phosphate to tyrosine on response protein

what does cell response depend on

type of response proteins inside the cell

what is a phosphotyrosine?

phosphorylated region outside the catalytic site

how are intracellular events initiated?

proteins bind to phosphotyrosine