APK 2105C Lecture Notes - Lecture 32: Prostaglandin E2, Rofecoxib, Cytochrome C Oxidase Subunit Ii
5 Jun 2018
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Chapter 5, Lecture 2
Chemical Messengers
• Classes of chemical messengers
Class
Chemical Property
Location of Receptors
on Target Cell
Functional
Classification
Amino acids
Lipophobic
Plasma membrane
Neurotransmitters
Amines
Lipophobic
Plasma membrane
Paracrines,
neurotransmitters,
hormones
Peptides/proteins
Lipophobic
Plasma membrane
Paracrines,
neurotransmitters,
hormones
Steroids
Lipophilic
Cytosol
Hormones
Eicosanoids
Lipophilic
Cytosol
Paracrines
• Peptide/protein messengers
o Most chemical messengers are polypeptides
▪ Peptide = < 50 AAs
▪ Protein = > 50 AAs
o Hydrophilic = water soluble, not fat soluble
o Receptors located on the plasma membrane (not fat soluble)
o Synthesis and release
▪ Synthesis is same as other proteins (transcription and translation)
▪ Release = proteolytic enzymes in the golgi or vesicles create the final
product
• mRNA goes into rough ER
• Travels in lumen of rough ER
as prepropeptide
• Reaches smooth ER and
breaks off into propeptide
• Propeptide is taken up by
golgi apparatus
• Goes through golgi until it
reaches other side and then
gets cleaved off into
secretory vesicle (propeptide
inside)
• The AAs are cleaved into peptides and then released by
exocytosis
• Steroid messengers
o Derived from cholesterol
o Always function as hormones
o Lipophilic
▪ Receptors located mostly in the cytosol
▪ Few examples of receptors on the membrane (estrogen)
o Synthesis and released
▪ Synthesized in smooth ER or mitochondria
▪ They are membrane permeant, they cannot be stored in cells which
secrete them—leak out of cell as soon as they’re made
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