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Cytokine Signaling
Types of receptors
• Protein tyrosine kinase receptors with intrinsic kinase activity– Insulin, EGF, PDGF, CSF-1 etc.
• Protein serine kinase receptors with intrinsic kinase activity– MIS, TGF, activin, inhibin etc.
• Receptors without intrinsic kinase activity– This is the large, heterogeneous group called the
cytokine receptor super family• G-protein coupled receptors and ion-gated
receptors
Types of receptors
Protein tyrosine kinase receptors
PTK receptor activating MAP kinase pathway
PTK receptor activating Pi-3 kinase pathway
SH2 domain containing protein: recognition of phosphotyrosines
PTK signaling: 1o and 2o signals
Cytokine signaling mechanisms
• Cytokines represent a diverse number of molecules.
• The super family of cytokine receptors more specifically refers to those cytokines that signal via the Jak-STAT pathway
• These include Interleukins 2, 3, 4, 5, 6, 7, 9, 11, 12, 13, & 15, and G-CSF, LIF and the interferons
• In addition, growth hormone, prolactin, erythropoietin, leptin, thrombopoietin
• Many growth factor signal pathways cross-communicate with the STAT pathway.
General scheme for all MAP-kinase pathways
Receptor activation of intracellular signaling pathways
PTK vs. cytokine pathways
G-protein coupled receptors
Cytokines and Leydig cells
Overview and significance of Immune-endocrine interactions
in the regulation of Leydig cell function
Immune-Endocrine control of Leydig cell function