MOLECULAR ENDOCRINOLOGY AND IMMUNOLOGY ECTURE 7 - Mechanism of action of growth hormone and prolacti Growth hormone: general actions; receptor; signal transduction; IGFs Prolactin: actions on mammary gland; other actions; receptor; signal transduction Mechanism of action of cytokines
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MOLECULAR ENDOCRINOLOGY AND IMMUNOLOGY
LECTURE 7 - Mechanism of action of growth hormone and prolactin
Growth hormone: general actions; receptor; signal transduction; IGFs
Prolactin: actions on mammary gland; other actions; receptor; signal transduction
Mechanism of action of cytokines
The GH-IGF-Somatic axis
GH RECEPTOR
• First cloned (as cDNA) from rabbit and then human liver (Leung et al 1987)
signal
extracellular
transmembrane
intracellular0 247 620
Shown to be the “real” receptor by specificity, and absence in patients with Laron dwarfism
Cytokine receptors
OVINE GH-RECEPTOR HOMOLOGY MODEL
ReceptorReceptor
Intracellular actions
GH-RECEPTOR INTERACTION
JAK Kinases
Soluble tyrosine protein kinases, first named “just another kinase”. Subsequently “janus kinases” (because two apparent binding sites for ATP)
JAK1JAK2JAK3Tyk
GH Receptor and jak2
From: Herrington & Carter-Su (2001)
GH signalling
From: Herrington & Carter-Su (2001)
STAT = signal transduction and activation of transcription
STAT1-STAT5
In 3T3-F442A cells use of antisense knock-out of JAK2 or STAT5 eliminates GH actions. Depletion of MAPK pathway and p70s6 kinase pathway does not
Regulation of GH receptor–JAK2 signaling
From: Herrington & Carter-Su (2001)
The GH-IGF-Somatic axis
THE SULPHATION FACTOR/SOMATOMEDIN/IGF HYPOTHESIS
Inject hypophysectomized rat with GH: induces growth and metabolism of cartilage (including incorporation of 35SO4 into cartilage)
Incubate cartilage from hypox rat with serum from hypox rat + GH - no stimulation of cartilage metabolism
Incubate cartilage from hypox rat with serum from GH-treated rat -stimulation of cartilage metabolism
SO GH treatment leads to production of a factor in serum which can stimulate cartilage metabolism and growth
Insulin-like growth factor I and II
IGF I IGF II
Somatomedins
Non-suppressible-insulin-like-activity (NSILA)
Multiplication stimulating activity (MSA)
Sequence of IGF II
Sequences of insulin and IGFs compared
Precursors of insulin and IGFs
proinsulin
proIGF I
proIGF II
IGF II Insulin
3D structures of insulin and IGF
The GH-IGF-Somatic axis
Isaksson
The GH-IGF-Somatic axis
Endocrine control of mammary gland
Mammary gland development
Prolactin induces synthesis of the following proteins: