University:
Amherst College
Course:
BIOL 303 | Molecular Neurobiology: CURE
Academic year:

2022
Views:

32

Pages:

10
Author:

Rafael Werner

NGF and its receptor Levi-Montalcini and Hamburger • • An excess of nerves, and death of the failures # dying neurons in DRG ~ 1/size of receptor field – More death if target tissue reduced – Less death if more target added, OR – If retrograde transport is blocked • Nerve growth factor (salivary gland) – In pure form, decreases DRG death – Decreases death in other sensory neurons, but not all – Increases axonal/dendritic arborization Levi-Montalcini and Hamburger • Making a nervous system – Start with an excess of nerves – Death of the failures (and not failure to form) • # dying neurons in Dorsal Root Ganglia – – – – ~ 1/size of receptor field More death if target tissue reduced Less death if more target added, OR If retrograde transport is blocked Protein properties • NGF – Encourages neurite outgrowth in vitro – Larger precursor becomes smaller active product – Secreted (extracellular) protein – Made in target tissues, not in neurons Protein properties • Relatives – Brain derived Neurotropic Factor (BDNF) • Low concentrations • Complementary specificity – Others by molecular biology • Nerve cells bind NGF with low (109M) and high (10-11 M) affinity • TrK – Oncogene rearranged in a colon carcinoma – Only expressed in neural crest cells in vivo (but PC12 cells in vitro) – Tyrosine kinase • NGF induces autophosphorylation • Crosslinking experiment – Band created containing NGF and TrK – Another with p75 NGFR NGF Receptor • • • • Seven β strands with lots of twist and disulfide "knot" Sulfhydryls (extracellular protein) No visible N or C terminal Where does NGF bind to receptor? NGF structure (1BET) • Protein explorer (1BET) – (1BET) QuickView, Cartoon view – 1B8M (BDNF) • Note Dimer • Select :A, Display Only, Center/Cancel – Postulate variable regions (to explain specificity) • Variable regions – Advanced explorer/Seq3D/Display selected/Ball and Stick – Residues 29-35, 43-8, 92 • 1BET vs 1B8M – Spacefill; Color Polarity5 Ligand Receptor Interaction (1WWW) • NGF interacting as dimer • Dimer interface – Mix of hydrophobic and hydrophilic – Aromatic residue interactions • Protein Explorer (1WWW) – Select :w,:v ; display only – W spacefill, Polarity 5; V cartoon – Reset; Hide X,Y; W, V Cartoon, – Select/Spacefill: • Phe49, Trp99 • Trp21, Tyr52, Phe54; Phe86, Phe101 • Phe12, Trp76 – Edge/Pi interactions • • • TrkA: Binding domain an IgG fold (β sandwich) Two binding surfaces Central (conserved) patch – Conserved Arg103 – Phe327 stack, Carbonyl Hbond • Red residues (conserved) Ligand Receptor Interaction (1WWW) • • • • • • Protein explorer Quickviews (spin/water) Advanced explorer Contact surfaces :Y receptor; :W ligand Hide noncontact surface, show receptor atoms Interaction cont'd • N terminus of NGF visible!! • – Only in complex – Short helix, well defined • • • Buried in interface Both NGF and TrkA residues are not conserved Specificity surface Back/Reset View – Display/Cartoon; Color/N to C – Color/Temperature • Advanced Explorer/Contact Surfaces – :Y Receptor – Ser2,Ser3,HIs4,Pro5,Ile6,Phe 7, Arg9 Ligand

NGF and Its Receptor

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