ADAPTATION OF THE SECRETORY PATHWAY IN NEURONAL DIFFERENTIATION MODELS

DI GIUSTO, P; ALVAREZ, C; SAMPIERI, L

Salta

Congreso; Congreso SAIB/PABMB 2019; 2019

SAIB

Intracellular protein trafficking is essential for all eukaryotic cells. The secretory pathway targets proteins to the extracellular space and is responsible for protein and lipid transport among different cellular compartments. To allow membrane flow and maintenance of organelle size and cellular homeostasis a high degree of coordination in every step of intracellular trafficking is required. The role of the secretory pathway during cell differentiation is crucial and particularly special for neurons because they need to develop an extremely polarized phenotype which is accompanied by a large cell surface expansion, implying that an increase in plasma membrane protein and lipid synthesis and transport is required. Therefore, the secretory pathway must adapt to respond to this greater demand of its function. The mechanisms that regulate the expression of secretory pathway proteins in this type of cells have been poorly described. The CREB3 family of bZIP transcription factors, which comprises CREB3, CREB3L1, CREB3L2, CREB3L3, and CREB3L4, has been described to participate in cell differentiation in various tissues by regulating the secretory machinery. However, very little is known about their role in the nervous system. Our goal is to analyze the regulation of the secretory pathway and the participation of CREB3 transcription factors in neuronal differentiation models. To accomplish this, we used two cellular models: rat pheochromocytoma cells from a PC12 cell line, which respond to nerve growth factor (NGF) and in vitro cultured primary rat hippocampal neurons. Both models have been extensively characterized and widely used to study neuron development. We demonstrated, in PC12 cells, that NGF treatment induces an increase in the levels of transport proteins and Golgi complex size. Also, we found that CREB3L2 increases during NGF-induced differentiation and that MAPK and PKA signaling pathways, both regulators of neurite outgrowth, control CREB3L2 response to NGF. We observed that partial inhibition of CREB3L2 expression alters normal neurite outgrowth in response to NGF. Interestingly, we found that, during the early development of hippocampal neurons in vitro, levels of transport proteins and CREB3L1 increase. In this context, blocking CREB3L1 transcriptional activity impairs normal neurite development and Golgi morphology. Altogether, these data indicate that during neuronal differentiation an adaptative response of the secretory pathway occurs, presumably mediated by CREB3 factors and that this response is required for proper development, highlighting a novel role for these transcription factors in neuronal cells.