Chapter 4
Extracellular signals:
Hormones, cytokines and growth factors
Objectives
• Understand the general role of Hormones,
Cytokines, Growth Factors and
Neurotransmitters
• Learn the abbreviations for the general
molecules in each class
• Know one example of a function for each
group of signals
Hormones
• Small water soluble molecules
– Cannot cross plasma membrane
– Must target cellular receptor
– Examples
• Histamine
• Epinephrine
Hormones
• Peptide Hormones
–
–
–
–
Water soluble
Stored in vacuoles
Pro-peptides
Examples
• Insulin
• Glucagon
• LH (luteinizing
hormone)
• FSH (follicle stimulating
hormone)
Hormones
• Lipophilic
molecules
(extracellular)
– Still need a
receptor
– Prostaglandins
• Synthesized
from
arachidonic
acid
– Usually have to
do with
inflammation
Hormones
• Lipophilic molecules (intracellular)
– Receptors are on the inside of the cell
– Steroid hormones
– Examples
• Testosterone
• Progesterone
• Thyroxine
Hormones
• Plant hormones (for Joe!!)
– All extracellular signals
– Auxin
• Young leaves and seeds
• Very diverse effects
– Cytokinins
• Developing seeds
– Gibberellins
• Young shoots and seeds
• Flowering and germination
– Abscisic acid
• Roots and mature leaves
• Stromal closure
– Ethylene
• Gas
• Fruit ripening
Cytokines
• Very large family
of peptides
• Range in size
from 10-70 kDa
Name of Group
Examples
Notes
Interferons
IFN-α
IFN-β
IFN-γ
Viral infection
response
Interleukins
IL-1 to IL-35
Some with more
than one isoform
Cell growth and
differentiation
Tumor necrosis
factors
TNFα
TNFβ
TGFβ
Inflammatory
response
Chemokines
MIP-1α
NAP-2
RANTES
Leukocyte location
signals
Colony stimulating
factors
M-CSF
G-CSF
GM-CSF
Development of
bone marrow
Cytokines
• Interleukins
– 37 family members
– IL-x
– Many different sizes
– Many different receptors
– Many different functions
• Immune response and maturation
• Can activate themselves or nearby cells
Cytokines
• Interferons
– Type I
• IFN-α, INF-β, IFN-Ω
– Type II
• INF-γ
– Anti-tumor properties?
• Tumor necrosis factors
– TNF-α and TNF-β
• Works closely with IFN and causes necrosis of tumors
(hence the name!!)
Growth Factors
• Platelet-derived growth factors (PDGF)
– Induces cell migration & proliferation
• Fibrosis and arteriosclerosis
• Epidermal growth factor (EGF)
– Various functions
• Fibroblast growth factor (FGF)
– Cell proliferation, migration and motility
• Proto-oncogenes?
Neurotransmitters
• Stored in vesicles, released upon Ca2+ stimulation
• Small Molecules
– Acetylcholine, GABA, dopamine, γ-aminobutyric acid
– Glycine, glutamate, ATP and adenosine
• Neuropeptides
– Substance P, Endorphin, vasopressin