Assessing the Co-Chaperone and Synaptic Protein DNAJC5 as a Therapeutic Target in Alzheimer’s Disease (P1-6.010)

Abstract

<h3>Objective:</h3> Assess the therapeutic potential of <i>DNAJC5</i> in Alzheimer’s disease (AD). <h3>Background:</h3> <i>DNAJC5</i> encodes cysteine-string protein alpha (CSPα), whose mutations cause adult neuronal ceroid lipofuscinosis (ANCL). ANCL is characterized by endolysosomal dysfunction, synaptic loss, and protein aggregate accumulation, similar to AD. CSPα facilitates secretion of the neurodegenerative proteins tau, TDP-43, and α-synuclein and maintains synaptic integrity. Therefore, CSPα is a promising therapeutic target. <h3>Design/Methods:</h3> N2A695 cells stably expressing mutant <i>DNAJC5</i> or knocking down endogenous <i>Dnajc5</i> were analyzed through immunoblotting and ELISA for APP processing and Aβ production. Brains of ANCL patients and <i>Dnajc5</i>+/−; 5xFAD mice were assessed for amyloid pathology with immunohistochemistry. Transcriptomics from ANCL, AD, and control brains was analyzed for differentially expressed genes (DEGs). The Clue.IO database was used to identify potential targets for gene therapy or pharmacological intervention. <h3>Results:</h3> ANCL-patient brains exhibited low soluble or insoluble Aβ levels, but intra-neuronal Aβ accumulation. They exhibited reductions in synaptic protein levels (SNAP-25, Synaptobrevin, Syntaxin 1, and Synaptophysin). Transcriptomic analysis of ANCL-patient brains showed reduced <i>TSPAN14</i>, which facilitates ADAM10 maturation, elevated <i>APH1B</i>, a γ-secretase subunit, and elevated <i>GSAP</i>, the γ-secretase activating protein. There were 67 upregulated and 15 downregulated transcripts associated with processes essential for synaptic function, including the MAPK cascade (<i>FYN</i>, <i>SOS1</i>), dendritic spine organization (<i>FYN</i>), and endosomal vesicle fusion (<i>VPS11</i>, <i>VPS39</i>). Clue.IO identified heat-shock protein inhibitors and an opioid receptor antagonist (BNTX) as potential pharmacological agents to counteract the effects of mutant <i>DNAJC5</i>. AD patients and 5xFAD mice exhibited reduced <i>DNAJC5</i> expression. Preliminary results from <i>Dnajc5</i>+/−; 5xFAD mice showed increased plaques in the corpus collosum and hippocampus. N2A695 cells expressing <i>DNAJC5</i> mutants showed increased Aβ while <i>DNAJC5</i> knockdown decreased Aβ. <h3>Conclusions:</h3> Low levels of CSPα alter Ab secretion and dysregulate genes and synaptic proteins, suggesting that increasing CSPα levels could reduce Aβ and improve synaptic function. <b>Disclosure:</b> Dr. Rosene has nothing to disclose. Dr. Nykanen has nothing to disclose. Kevin O’Dell has nothing to disclose. Ms. Nunez has nothing to disclose. Dr. Harari has nothing to disclose. John Cirrito has nothing to disclose. Prof. Sands has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for M6P Therapeutics. Prof. Sands has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Amicus. Prof. Sands has stock in JAYA Biosciences. The institution of Prof. Sands has received research support from JAYA Biosciences. Prof. Sands has received intellectual property interests from a discovery or technology relating to health care. Bruno Benitez has nothing to disclose.