General Principles of Cell Signaling Flashcards
Three types of Cell Signaling
- sharing info via gap junctions
- contact-dependent signaling
- signaling via secreted molecules
Example of sharing info via gap junction
Glucagon receptors
-not uniformly distributed on liver cells
-connexins (=gap junctions) couple liver cells
Signal: cAMP (cyclic adenosine monophosphate)
Function: Synchronize the response to glucagon
For gap junctions, each cell has one half-pore that makes a whole pore between the two cells when connected. What makes up a half-pore?
6 connexin molecules
Example of Contact-dependent signaling
Leukocyte adhesion prior to transmigration n inflammation
Signal: Glycoproteins on leukocyte
Receptor: Adhesion proteins on endothelial cells
Function: Attract and guide leukocytes to a site of injury
Sharing info by a gap junction requires the cells to be….
touching and connected
In contact-dependent signaling, signaling and target cells are close together or far apart/
Close together
Example of Signaling via secreted molecules
Signals: hormones, neurotransmitters (ex - epinephrine, acetylcholine, erythropoietin,etc.)
Receptors: alpha- and beta-adrenergic receptors, nAchR, mAchR, erythropoietin receptors,etc.
Function: constriction, relaxation, secretion, growth, etc.
Endocrine
Signaling molecule is transported via the circulation
Neuroendocrine
- similar to endocrine
- signaling cell is a neuron
paracrine
- signaling molecule diffuse to nearby cell
- close by, but not identical cells (different cell types)
neurotransmitter
- similar to paracrine
- signaling cell is a neuron
autocrine
- similar to paracrine
- signaling cell is the target cell
- to cell of same type (or even the same cell that released the signal) -> like patting yourself on the back
T/F: V1 and V2 are identical.
False.
They are similar, but not identical.
Endocrine Signaling Example
Anti-diuretic homone (ADH) = Argenine-Vasopressin (AVP)
Signal: ADH/AVP
Receptors
- V1 vasopressin receptor on smooth muscle cells
- V2 vasopressin receptor on kidney collecting duct cells
Function
-Respond to low blood volume and high blood osmolarity w/ water retention and vasoconstriction
When blood volume is low and blood osmolarity is high, what is the purpose of anti-diuretic hormone/ argenine-vasopressin?
Why is this important?
Purpose:
- kidneys =water retention
- blood vessels: vasoconstriction
Important: keeps blood pressure up and keeps brain oxygenated
Where is ADH/AVP secreted?
From Posterior Pituitary
Paracrine Signaling Example
Histamine-induced vasodilation via nitric oxide (NO)
Signal: Histamine and NO (both act paracrine)
Enzyme: Histamine receptors and guanylyl cyclase
Function: Vasodilation as part of an inflammatory response
Neuronal signaling example
Neuromuscular Junction
Signal: Acetylcholine
Receptor: Nicotinic acetylcholine receptor
Function: Voluntary muscle contraction
Synaptic Signaling
- signal reaches many cells
- low concentrations of signaling molecule are needed to activate the target
Endocrine Signaling
- signal reaches only specific cells
- high concentrations of signaling molecule are needed to activate the target
Signaling molecules are chemically very diverse and can include…
- proteins
- peptides
- fatty acid derivatives
- amino acids
- cholesterol derivatives
- small molecules
- dissolved gases
- ions
Difference between water-soluble and lipid-soluble signaling molecules (=drugs)
water-soluble = reach receptors on outside of cell
lipid-soluble = reach receptors on inside of cell
In regards to drugs, what does solubility define?
- the body space in which the drug is diluted
- the location of receptors that are reached
Three Types of Target Molecules
Cell-surface receptors
Intracellular receptors
Intracellular enzymes
Example of a Cell-surface receptor
ADH/AVP
signal: ADH/AVP
Receptors: V1 and V2 vasopressin
Function: Respond to low blood volume and high blood osmolarity with water retention and vasoconstriction
Intracellular Receptor Example
Aldosterone control of plasma K+ concentration
Signal: aldosterone
Receptor: aldosterone receptor
Function:
- Respond to a high [K+] in plasma with K+ excretion via the collecting duct of the kidney
- increases Na+ and water retention
Intracellular Enzyme Example
Vasodilation via nitric oxide (NO)
Signal: NO
Enzyme: Guanylyl cyclase
Function: Vasodilation as part of inflammatory response
