[biological_process] cellular response to nerve growth factor stimulus <sep> microtubule depolymerization <sep> negative regulation of microtubule depolymerization <sep> negative regulation of microtubule polymerization <sep> negative regulation of neuron projection development <sep> neuron projection development <sep> positive regulation of microtubule depolymerization <sep> positive regulation of neuron projection development <sep> regulation of microtubule polymerization or depolymerization