Cell to Cell Signaling

Gap junctions

Functional Synctium

Connexins: Connect & Share Cytoplasm

Found inbetween neurons, smooth muscle cells, cardiac tissue, bone celle.

Example: CAMs

Bind to surface of cell membranes

• Neurocrines: Chem made by neurons
• Neurohormones: chem made by neurons made in hypothalamus

Neuromodulators: chem made by neurons to alter 2nd messenger response.

Control:

• cell development,
• Cell differentiation,
• & Immune response

Distance: both short and long distance

• Extracellular First messengers
• Receptors
• Intracellular Second Messengers

• Agonist: attaches and mimics first messenger
• Ex: Ephederine

• Antagonist: get in way of receptors, deactivating them.
• Ex: Beta blockers to lower BP

• Down Regulation
• Desensitization

Receptors are still there but not the active site.

Up-regulation

An increase of sensitivity of binding sites + more FM

Paracrines: Chem made by neurons, signal neighbor cells

Autocrines: Chem made by themselves for itself.

mediator cells between FM and SM found in cell membrane or cytosol

Stimulate a cell response

• Hormones
• Neurotransmitters
• Neurohormones
• Local Chemical Mediators
•      a. paracrines
•      b. autocrines
•      c. Cytokines

receptors in cell membrane.

Lipophobic WILL NOT dissolve in lipid bilayer

receptors in cytoplasm or nucleoplasm of cell

Amplifier enzyme activates a secondary messenger

Process by which stimulus is transformed into cell response.

Nicotinic attaches in place of ACH (adrenaline)

Open/close by a receptor that attaches and acts as ion channel directly

• Receptors
• Ions
• Channels
• Enzymes

RICE

Protein Kinases except for one guanylyl cyclase activity

• Binding of messenger to receptor on cytoplasmic side of PM.
• Tyrokinase = Activated = Insulin Receptor Attaches
• Autophosphorylates
• Bind and activate other proteins
• Glut 4 activated to insert into membrane Guanylyl Cyclase funcs as receptor & Cyclic-GMP as second messenger

• Alpha --> GDP & GTP
• Betta & Gamma --> Help anchor Alpha

• Binding of FM Occurs On receptor
• Activated receptor = higher affinity for Alpha
• Alpha disassociates from betta/gamma
• Allows alpha to bind to other PM proteins
•          (ion channel or enzyme thus called effector proteins)
• G-protein cples recept to effector proteins
• Activated effector GTP-ase to cleave GTP into GDP + P1

This renders alpha subunit inactive allowing to recombine w/ its betta and gamma sub units.

• Bound to inactive receptors is a protein complex located on cytoplasmic side of Plasma membrane.
• (alpha beta gamma)

• Remove the First Messenger(Brk dwn FM enz)
• Inactivate Receptors(PO4/Endo/ClathPIT)
• Removal of second messenger
• (rmvl of F.M or break down 2nd Messenger)

GASES!

THESE DIFFER FROM OTHER CHEMICAL MESSENGERS

• M binds 2 inactive receptors in nucleus
• Gene Transcription
• Diffuses out capillaries/across P.M Binds 2 rec in nucleus
• Transcription factors
• mRNA move out of nucleus synthesizes on ribosomes
• Cells ultimate response

• Bind 2 extracellular portion on PM
• Secondary messenger in cytoplasm activated
• Diffuses through PM
• Protein Kinase
• Cell Response

Receptors/channels: ex Nicotinic receptor

Receptor/Enz: ex: Guanacyc. Tyr. Kinase GMP

Receptor/CAM: ex

• a. Receptors that themselves function as ion channels.
• b. Receptors that themselves function as enzymes.
• c. Receptors that are bound to and activate cytoplasmic JAK kinases.
• d. Receptors that activate G proteins, which in turn act upon
• effector proteins—either ion channels or enzymes—in the plasma membrane.

• lipid-soluble messengers)
• Function in the nucleus as transcription
• factors to alter the rate of transcription of particular genes.