Brief Review – Growth Factors and Receptors most growth factors are secreted receptors are transmembrane proteins 3 major features: extracellular domain transmembrane region intracellular domain where, when, and how they are expressed determines their biological function

FIGURE 26-3: Schematic structures of receptor protein tyrosine kinase (RPTK) families. RPTKs can be divided into different families according to the structural features in the extracellular domain. Following the extracellular domain are the transmembrane and intracellular domains; the latter contains the catalytic domain. (Adapted from Blume-Jensen & Hunter, 2001 with permission.) Copyright © 2012, American Society for Neurochemistry. Published by Elsevier Inc. All rights reserved.

FIGURE 26-4: Nonreceptor protein tyrosine kinase (NRPTK) families FIGURE 26-4: Nonreceptor protein tyrosine kinase (NRPTK) families. The family members are shown to the right and family name to the left of each NRPTK. Inset indicates the PTK catalytic domain and other domains for the regulation of localization and function. Kinases listed in bold have been associated with malignancies in humans and/or animal models. (Adapted from Blume-Jensen & Hunter, 2001 with permission.) Copyright © 2012, American Society for Neurochemistry. Published by Elsevier Inc. All rights reserved.

FIGURE 26-5: SH2, SH3 and phosphotyrosine binding (PTB) domain-containing signaling proteins. SH2, SH3 and PTB domains are important molecular ‘adhesives’. These domains are found in enzymes and play important roles in the regulation of enzyme function. They also are found in proteins lacking any apparent catalytic domain, in which case they may serve as adaptor proteins, assembling signal-transduction complexes. The PTB domain of insulin receptor substrate-1 (IRS-1) shares a low degree of homology with the one on SHC. The black circle indicates a myristic acid moiety. PLC, phospholipase C; PI3-kinase, phosphatidylinositol-3-kinase; PTP, protein tyrosine phosphatase; PH, pleckstrin homology; SHP, SH2-containing PTP; Grb, growth-factor-receptor-binding protein. Copyright © 2012, American Society for Neurochemistry. Published by Elsevier Inc. All rights reserved.

Brief Review – Receptor Activity intracellular, or catalytic, domain has kinase activity kinases add phosphate groups to (phosphorylate) specific amino acids ATP-binding Phospho-transferase ATP P Amino Acid P ADP

Consequences of RTK activation GROWTH FACTOR PIP3 PIP3 RTK SOS Grb2 RAS RAS P P P PI3K p85 p110 Akt PDK1 Raf P MEK P P GSK3 P P P P BAD NF-ĸB MDM2 p70S6K FKHR P ERK PROLIFERATION CELL SURVIVAL PROTEIN SYNTHESIS . Aaronson, Growth factor and receptor tyrosine kinases. Sci. STKE 2005, tr6 (2005).

Intracellular Signaling begins with autophosphorylated or transphosphorylated amino acids on the receptor Phosphorylation recruits other proteins to the receptor Amino acids surrounding the phosphorylation site determine which proteins are bound… 4 major protein interaction domains: SH2, PTB, SH3, PH Membrane -Tyr P Kinase Domain -Tyr P

TABLE 26-1: Specificity and Affinity of SH2, Phosphotyrosine Binding (PTB) and SH3 Domains Copyright © 2012, American Society for Neurochemistry. Published by Elsevier Inc. All rights reserved.

Basics of Amino Acid Structure

Basics of Protein Structure Primary Structure = “beads on a string” Quaternary Structure = specific folding creates domains, or “units” of the protein

SH2 domains SH2 = src homology 2 was first identified as a 100 amino acid region of homology (“sameness”) in the src tyrosine kinase specifically recognizes phosphorylated Tyrosine 2 classes of SH2 domain-containing proteins… - have enzymatic activity (like Src) - don’t have enzymatic activity Those with no enzymatic activity bind other proteins to the receptor…adaptor molecules

SH2 domain specificity specificity is determined by the amino acids C-terminal to the phospho-Tyr in most cases, it is the amino acid at position +3 that determines specificity Hydrophobic amino acid Science, Vol 278, Issue 5346, 2075-2080 , 19 December 1997

PTB domains phosphotyrosine binding domains recognize amino acids N-terminal to the phospho-Tyr PTB-containing proteins also participate in hormone signaling any amino acid Science, Vol 278, Issue 5346, 2075-2080 , 19 December 1997

SH3 domains src homology 3 domains recognize amino acid sequences rich in Proline (Pro-rich) Is a more general protein-protein interaction motif… many cytoskeletal proteins contain it any amino acid Science, Vol 278, Issue 5346, 2075-2080 , 19 December 1997

PH domains pleckstrin homology domains recognize phospholipids (components of the plasma membrane) Science, Vol 278, Issue 5346, 2075-2080 , 19 December 1997

Protein-Protein Interactions and Receptors Proteins with many different interaction domains can bind to growth factor receptor family members Protein-protein interactions connect receptors to their intracellular signaling networks Figure 6.9 The Biology of Cancer (© Garland Science 2007)

Receptors bind other Kinases, and Adaptor Proteins Figure 6.10a The Biology of Cancer (© Garland Science 2007)

EGFR and the Ras Pathway SOS Grb2 RAS P P Raf P MEK Grb2: adaptor protein that binds to phosphorylated Tyr on EGFR using its SH2 domain P ERK PROLIFERATION CELL SURVIVAL . Aaronson, Growth factor and receptor tyrosine kinases. Sci. STKE 2005, tr6 (2005).

PI3K Target(s) PI3K phosphorylates PIP2 to make PIP3 PIP3 is now a binding site for Akt… Figure 6.19a The Biology of Cancer (© Garland Science 2007)