(Diversity Supplement) Alterations in the axon initial segment (AIS) are key pathophysiologies in various neurodegenerative diseases, including diabetes. Shortening of AIS length has been shown to lower neuronal excitability and is also implicated in cognitive impairment in type 2 diabetes and Alzheimer's disease. However, the cellular and molecular mechanisms of how these domains are altered in disease conditions remain poorly understood. This critical gap in knowledge limits the field's ability to manipulate the AIS for treatment. In order to fill this significant gap in our knowledge, the parent grant (R01 NS107398) tests the hypothesis that methylglyoxal (MG) disrupts AIS protein complexes via calpain activation and inhibits nervous system function. The current diversity supplement proposal seeks to elucidate more detailed mechanisms that lead to AIS shortening. The overall objective of this application is to identify a critical cellular mechanism that activates calpains in response to MG increase. The prior studies and preliminary data provided here have identified endoplasmic reticulum (ER) stress as a potential mediator for calpain activation and AIS shortening induced by MG increase. The hypothesis is that sublethal increase of MG induces ER stress, leading to calpain activation and AIS shortening. We will test this hypothesis via two Specific Aims.
Aim 1 : Test the hypothesis that, independent of MG increase, sublethal levels of ER stress cause calpain activation, AIS shortening, and neuronal network dysfunction.
Aim 2 : Test the hypothesis that inhibition of ER stress prevents MG-induced calpain activation, AIS shortening, and neuronal network dysfunction. This application is conceptually innovative, as we propose that ER stress is a key mediator of AIS shortening and neuronal dysfunction induced by MG. Innovative use of multi-electrode arrays will determine the effects of induced ER stress and increased MG together with ER stress inhibition on neural network function. The proposed research is significant, because completion of the aims will validate ER stress as potential targets for translational research aimed at treatments for comorbid cognitive impairment in type 2 diabetes. These results also have potential to impact a wide variety of neurodegenerative conditions, such as Alzheimer's. In addition to the scientific work, the important aspect of this diversity supplement is to support the career development of an African American female MD/PhD student. Her career goal is an independent physician scientist studying changes in neural transmission and cognitive defects caused by neurodegenerative diseases. Cognitive disorders disproportionately affect African Americans, yet African Americans are underrepresented in the scientific workforce. To address the inequity in heath research and clinics, it is critical to diversify the field. Thus, the proposed work and mentoring activities in this diversity supplement will ultimately provide a sustained and powerful influence on the field of neurodegenerative diseases.
Disruption of the axon initial segment in neurons is associated with cognitive impairment in type 2 diabetes, in which the glucose metabolite methylglyoxal is elevated. This diversity supplement application together with the parent R01 grant will elucidate the mechanisms of how methylglyoxal affects axon initial segment and neuronal function by identifying a critical cellular mechanism involved in this process. The proposed research is relevant to public health because it is expected to provide critical knowledge of nervous system pathophysiology needed to establishing novel treatments for cognitive impairment while training a future physician scientist to diversify the research field.
