Bio 171 Cell signaling

Cell junctions

gap junctions in animal cells, plasmodesmata in animal cells

• cell junctions are protein channels that link the cytoplasm of animal cells and allow ions to flow through

• these in plant cells are found in the cell walls

cell to cell recognition

a ligand embedded in the plasma membrane binds to a receptor that is on the plasma membrane of another cell

• these interactions are direct, important in development (also involve glycoproteins)

paracrine signaling

local signaling, cells that are adjacent to each other with receptors are involved. a ligand is released and locally diffuses away from high to low concentration, they bind to receptors on an adjacent cell

autocrine signaling

like paracrine except the ligand binds to a receptor on the same cell that released the ligand

endocrine signaling

long distance signaling, a ligand enters the blood stream and diffuses throughout the body

synaptic signaling

both local and long distance, occurs at a synapse between a nerve axon and target cell

• short distance

• very specific

• pre synaptic cell through synaptic vesicles will release ligand into synaptic cleft which the post has receptors for

• this receptor is an ion channel

intracellular receptors

receptors inside the cell

• hydrophobic lipids cannot enter the cell (steroids for example))

• these ligands are brought in through receptor mediated endocytosis

• where is the receptor: in the cytoplasm, it binds to the ligand, the receptor undergoes a conformational change

• nuclear localization signal is revealed which allows the complex to be carried through the NPC

• receptor binds to DNA causing gene expression

• CC exposes NLS → transported to nucleus → binds to DNA → upstream particular genes → expressed → RNA exported from nucleus → protein translation 

• How is it turned off? concentration of ligand lowers, receptor disassociates, changes conformation, exported from nucleus