Which of the following processes has most likely been disrupted?
A 3-year-old boy with a history of unexplained fever, lack of perspiration, the absence of response to noxious stimuli, and self-mutilating behavior is diagnosed with congenital insensitivity to pain with anhidrosis. Genetic analysis shows a missense mutation of the tyrosine kinase domain of the TrkA gene. Assume this is the only signaling defect in this patient.
A. Binding of nerve growth factor to its receptor B. Formation of TrkA homodimer in response to nerve growth factor C. Phosphorylation of downstream molecules in response to nerve growth factor D. Retrograde transport of nerve growth factor from nerve terminals E. Synthesis of nerve growth factor
The answer to this is letter C. Phosphorylation of downstream molecules in response to nerve growth factor. This question is asking what are prevented and C is the answer to this. The receptor component does not show any sign of mutation which means that the ligand will still have the ability to work with the receptor.
Take note that the kinase part is already mutated. When the right process does not occur, this means that the molecules that pass down that path will not go through the proper process anymore.
Phosphorylation of downstream molecules in response to nerve growth factor-https://hmg.oxfordjournals.org/content/10/3/179.fullnerve growth factor (ngf) supports the survival of sympathetic ganglion neurons and nociceptive sensory neurons in dorsal root ganglia derived from the neural crest and ascending cholinergic neurons of the basal forebrain. human trka (also named ntrk1) was isolated from a colon carcinoma as a potential new member of the tyrosine kinase gene family and expression of trka(trk) was later found in the nervous system. trka is a receptor tyrosine kinase which is phosphorylated in response to ngf . the binding of ngf to trka stimulates homodimer formation and activation of tyrosine kinase activity. phosphorylated tyrosine residues in the trka cytoplasmic domain serve as anchors for binding downstream signaling molecules.