Epithelial Cells.txt

• author "JLeezy"
• tags "PSL"
• description "Lectures 4-8"
• fileName "Epithelial Cells"
• freezingBlueDBID -1.0
• Epithelial Cells
• Transport and secretory cells

• Apical: flat side that interacts with lumen
• Basolateral: rest of the cell's surface, interacts with blood/ECF

Transcellular is through cells, paracellular is between them (via tight junctions).

• Nutrients begin in lumen
• Na+/K+ pumps create Na+ concentration gradient (Na+ goes out of cells)
• Na+ gradient powers active transport of nutrients into cells via apical side
• Nutrients exit cells via passive carrier proteins on basal side

Thick mucus secretions and salty sweat.

• 1: A large decrease in Cl- absorption (mutant CFTR) --> increase in NaCl concentration on airway surfaces --> impedes natural antibiotics, leading to more infections
• 2: A large increase in Na+ absorption (no CFTR, no ENaC inhibition) --> water follows solute --> low airway surfaces liquid volume --> more infections
• 3: No CFTR-mediated HCO3- transport --> without HCO3- being secreted into the airways, pH gets too acidic (?) or causes a lack of defensins (?) --> more infections

Anion (Cl-) channel. Mutated in CF. Inhibits ENaC channel when working properly.

Na+ channel

• Exocrine: secretion into lumen
• Endocrine: secretion into bloodstream (long-range)

Secretory gland for saliva

Cl- enters cell via basolateral side and exits via apical side (into lumen); water follows solute.

These proteins are made on the rough ER, sent to the Golgi, then the plasma membrane.

• Add labeled amino acids to pancreatic cells for only three minutes to see where proteins that were synthesized during those three minutes go.
• 3 min: rough ER
• 10 min: Golgi
• 30 min: ready for secretion @ membrane

Pores that trap growing polypeptides halfway across the lipid bilayer. Periodically open during the protein's growth to give it a chance to stay in cytosol or head to the membrane.

Cover vesicles and help with curvature AKA formation of the vesicles.

• Proteins that assist with vesicle fusion.
• v-SNARES: In the Vesicle, bind to t-SNARES
• t-SNARES: Extend from vesicle's Target location

• Endocrine agents, AKA hormones, transmit signals over long distances
• Paracrine agents affect nearby cells

• Kd=[L][R]/[LR]
• Smaller Kd means more sensitive signal reception.

• Agonists are ligands that are activators
• Antagonists are ligands that are inhibitors

Na+ (and some Ca++) channel that requires two Ach molecules to bind for it to open. Nicotine can do the function of Ach.

Ligand binds GPCR --> activates G-protein --> β and γ subunits head off to open a K+ channel and inhibit some Ca++ channels --> α subunit activates/inhibits adenylyl cyclase --> adenylyl cyclase increases/decreases cAMP levels --> 4 cAMP molecules activate PKA complex

Ligand binds GPCR --> activates G-protein --> β and γ subunits head off to open a K+ channel and inhibit some Ca++ channels --> α subunit activates PLC --> PLC hydrolyzes (splits) PIP2 into IP3 and DAG --> IP3 releases Ca++ from the ER, DAG activates PKC

Protein that requires 4 Ca++ molecules to bind. Once activated, calmodulin can binds to and activate other proteins.

• Receptor: desensitization, down regulation
• G-protein: GTPase, lipid modification
• Second messengers: elimination of second messengers from cell

Norepinephrine binds β-receptor --> G-protein, adenylyl cyclase, cAMP, PKA --> PKA phosphorylates SNARES, causing them to fuse and secrete their proteins

IP3 releases Ca++ from the ER. This Ca++ activates Cl- channels and transporters, allowing Cl- to leave the cell. Water follows solute - voila! Salivation!

Constant activation of G-proteins (and thus adenylyl cyclase --> cAMP --> PKA), and PKA keeps CFTR activated.

Large class of intracellular receptors that control hormones and nutrients as signals. Each has three sections: activation, DNA binding, and ligand binding.

• A simple (just has an α subunit) G-protein that activates MAP kinase.
• *Some cancers are caused by a mutated Ras that results in continual activation.

Regulates the entire cell cycle.

• Once activated (ligands bind) they dimerize, and then activate Ras with the classic GDP --> GTP.
• *No second messengers in this pathway.