Nörojenik yazılım faktörünün kortikal nöronlardaki depo-işletimli kalsiyum girişi üzerindeki kontrolü

Neurogenic differentiation factor 2 (NEUROD2) transcription factor, a member of basic helix-loop-helix transcription factors, is a factor with essential roles in brain development. Upon calcium binding, NEUROD2 mediates its transcriptional role and promotes neurogenesis. Studies performed in our laboratory have identified genes that are targeted by NEUROD2, and verified that Stim1 gene is among the top targets of NEUROD2. My thesis is composed of three major parts. In the first part, I investigated the effect of NEUROD2 on its targets with known functions in calcium signaling. Specifically, I found NEUROD2 targets several genes present in Ca2+ / Calmodulin-dependent protein kinase (CaMK) pathway. Also, I investigated whether a suppression of Neurod2 expression causes defects in the transcription of its targets. In the second part, I focused on one specific target of NEUROD2 called Stim1. We confirmed NEUROD2 binding to a conserved sequence within the second intron of Stim1. Further, a suppression of Neurod2 expression by shRNA transfection was associated with upregulation of STIM1 protein and mRNA levels. Since STIM1 is a sensor of ER Ca2+ levels, I investigated the role of NEUROD2 in store operated Ca2+ entry (SOCE). I demonstrated that knockdown of Neurod2 caused an upregulation of neuronal SOCE, which was rescued by expression of shRNA-resistant form of Neurod2. In the last part of my experiments, I studied a potential regulatory mechanism of NEUROD2 activity. I demonstrated that NEUROD2 is composed of cytosolic and nuclear fractions. Further, the cytoplasmic fraction was associated with a higher molecular weight NEUROD2, most likely representing a post-translational modification (PTM). I tested whether this PTM was a SUMO moiety, however my results were inconclusive. Taken together, my results suggest that NEUROD2 acts as a general regulator of neuronal calcium signaling. Future experiments will focus on identifying specific mechanisms of how NEUROD2 influences SOCE.