Cell communication - C&M

intercellular

between cells

intracellular

inside cells

signaling cells

these cells release chemical signals called ligands

ligands

these interact with protein receptors in target cells:

• these & receptors SPECIFICALLY bind to each other

• aka signaling molecules

paracrine

move by diffusion through extracellular matrix

• synaptic signals & neurotransmitters

endocrine

signals from distant cells; typically produce a slower response w/ a long-lasting effect

• hormones

autocrine

a cell secretes a signal molecule that binds to receptors on its OWN SURFACE, leading to changes within that same cell

• cancer cells

• cell death signaling

• developing embryonic cells

direct signaling across gap junctions

this involves intracellular mediators that allow small signaling molecules to move b/t cells

• plasmodesmata — entire plant is a signaling network; only small molecules/ions can cross the gap

internal receptors

hydrophobic signaling molecules diffuse across the PM & interact w/ intracellular receptors:

• many are transcription factors that interact w/ DNA in the nucleus (regulate gene expression)

cell-surface receptors

• ion channel-linked

• G-protein-linked

• enzyme-linked

ion channel-linked receptor

gated ion channels form a pore through the PM that opens when the signaling molecules binds

ions flow into/out of cell:

• this flow changes the electrical charge difference across the PM

  • triggers a cellular response

G-protein-linked receptor

a ligand binds & activates G-proteins, causing a signaling cascade

ex. Vibrio cholera

• produces a toxin that modifies these receptors in the intestines

• leads to severe diarrhea, dehydration, & death

enzyme-linked receptors

a ligand binds & causes intracellular signaling cascades through enzymes

ex. growth factors/mutations

• lead to growth abnormalities like dwarfism or cancers

small hydrophobic ligands

• steroid hormones have similar chem. structs. to cholesterol

• can diffuse directly across the PM where they interact w/ internal receptors

water soluble ligands

these typically bind to cell-surface receptors

gas ligands

one example is nitric oxide:

• affected by nitroglycerin (treatment for heart disease) & Viagra

signal transduction

• ligand binds to a receptor

• signal is transmitted through the cell membrane & into the cytoplasm

• continues the signal

dimerization

2 receptors bind to each other to form a stable complex

signaling pathway

chain of events that happens after a ligand binds to a receptor & include:

• 2nd messengers

• enzymes

• activated proteins

signal integration

signals from 2 or more different cell-surface receptors merge to activate the same response in the cell

phosphorylation

method of intracellular signaling:

• phosphate group is added to residues of serine, threonine, & tyrosine (AAs)

  • kinase — enzyme that catalyzes the transfer of a phosphate group

second messengers

small molecules that propagate a signal (after ligand-receptor binding)

• cyclic AMP (cAMP) — activate/inactivate proteins in a cell; is terminated when an enzyme converts it to AMP

responses to the signal

• gene expression

• increase in cellular metabolism

• cell growth

apoptosis

cell death; signals are terminated by degradation of ligands or by other signals

• embryonic development — cells b/t fingers & toes undergo this

yeast

• single-celled

• can communicate by releasing a signaling molecule called a mating factor

• mating factor binds to cell-surface receptors in nearby cells

• stop normal growth cycles & initiate a signaling cascade

quorum sensing

a chemical language that bacteria use to communicate:

• autoinducers are released into the environment

• as the bacterial population grows, autoinducers increase

• at a certain concentration, the bacteria recognize that they’re part of a community & can coordinate their behavior

Bonnie Bassler

who is the professor from Princeton University that discovered quorum sensing?

Hawaiian bobtail squid

what is the name of the animal that uses Vibrio fischeri to camouflage itself from predators?

• reside in the light organ (room & board)

• uses quorum sensing to coordinate bioluminescence at night

  • looks like the moonlight