LEUCINE-RICH, GLIOMA INACTIVATED 1 (LGI1) PROTEIN DYNAMICS IN PRIMARY HUMAN ASTROCYTES IN RESPONSE TO INFLAMMATORY SIGNALS

Leucine-rich, glioma inactivated 1 (LGI1) is a secreted glycoprotein that functions as a scaffold between pre- and post-synaptic neurons with critical regulatory influence on excitatory synaptic signaling. While LGI1’s importance in neurons has been extensively studied, LGI1 is also abundant in astrocytes, where its role and activity remain elusive. As the initial step in our investigation of LGI1’s function in astrocytes, we first characterized the cellular distribution and dynamic expression profile of LGI1 proteins in primary human astrocyte cultures. We show that astrocytes express a glycosylated form of LGI1 resembling the functional version secreted by neurons. Subsequently, we examined whether these glycosylated LGI1 proteins are secreted and surface localized in astrocytes, using western blot analysis to detect its presence in secreted proteins collected from cell culture media or cell surface proteins isolated with biotin-labeling. In parallel, we seek to elucidate whether astrocytic LGI1 secretion or surface localization is controlled by stimulus-induced trafficking mechanisms, as observed in neurons. We found that exposing astrocyte cultures to a pro-inflammatory cocktail of TNFα, IL-1α, and C1q increased whole-cell LGI1 protein abundance, suggesting stimulus-dependent regulation of LGI1 expression. In our ongoing examinations, we expect inflammatory stimulation of astrocytes to upregulate LGI1 transcription, measured with RT-qPCR. Furthermore, we are investigating whether the increase in LGI1 protein abundance corresponds to elevated secretion and surface localization of LGI1 using western blotting and immunocytochemistry. Altogether, these results provide an instrumental characterization of LGI1 proteins in astrocytes that will inspire further exploration of its role in astrocyte physiology.