ESTROGEN AND PROGESTERONE MEDIATE DENDRITIC SPINE FORMATION THROUGH THE ACTIN REGULATORS CORTACTIN AND WAVE-1.

SANCHEZ, ANGEL MATIAS; UZAIR, IVONNE DENISE; FLAMINI, MARINA INES

Buenos Aires

Congreso; Reunión Conjunta de las Sociedades de Biología 2017; 2017

Pyramidal neurons from cortex and hippocampus have thousands of dendritic spines (DS) that form excitatory synapses. As a consequence, failures in DS formation can lead to an improper cognition, a common feature in neurodegenerative diseases like dementia. Actin nucleation is a fundamental process in DS formation and it depends on actin regulators. Among them, WAVE1 and Cortactin are key activators of the Arp2/3 complex, ultimate responsible for DS formation. Our previous research has established that 17β-estradiol (E2) and progesterone (P4) modulate several signaling pathways leading to WAVE1 phosphorylation and DS formation. However, the precise molecular mechanisms of this regulation remain to be elucidated. Therefore, we asked ourselves firstly, if Cdk5 Kinase and PP2A phosphatase regulate WAVE1 phosphorylation (their target protein) in response to rapid treatments with E2 and P4. Secondly, we evaluated if Cortactin phosphorylation was affected by the same treatments. To test our hypothesis, we employed primary culture of embryonic rat cortical neurons, immunofluorescence and western blot analysis. Our results showed that, after treatments with E2 or P4 (10nM, 20min), the number of DS was signifi-cantly increased (over a 50% vs. CON, p˂0,05), indicating that both hormones rapidly modi-fied neuronal morphology. The increase in the number of DS was prevented by Roscovitine, a Cdk5 inhibitor, and mimicked by Okadaic Acid, a PP2A inhibitor. These changes were accompanied by a significantly increase of the phosphorylation patterns of Cdk5Y15, PP2AY307 and WAVE1S397 after E2 and P4 stimulation. Furthermore, we also determined that Cortactin mediates DS formation via a Rac1/PAK1 cascade, after E2 and P4 treatment. As a conclusion, our results suggest that E2 and P4 exert a dynamic regulation of neurons morphology by inducing a rapid activation of Cortactin and WAVE1. E2 and P4 can promote DS formation and therefore they contribute to synaptic plasticity processes.