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