Proteomic analysis reveals APOE isoform-specific regulation of ribosomes in neural precursor cells

ApoE4 isoform contributes to increased risk for Alzheimers Disease (AD) over the life course of individuals. Much remains unknown about the biological pathways that connect APOE4 genotype with the development of pathology that eventually leads to AD, nor do we know how early in life these cellular alterations begin. To answer these questions, we derived neural precursor cells (NPCs) from induced pluripotent stem cells (IPSCs) that were CRISPR-edited at the APOE locus. We intended to characterize the protein expression landscape in the NPCs subsequent to targeted deletion of E4 from a parent IPSC line of APOE3/4 genotype. Differentially expressed proteins (DEPs) following mass spectrometric analysis were determined from the protein abundance fold change values obtained for each protein. Proteins which showed >1.5-fold difference with FDR adjusted P-value < 0.05 were considered differentially expressed. DEPs were mapped to the STRING database (v11.5) for retrieval of interacting proteins and functional enrichment. CRISPR-editing of E4 from the parent line revealed 98 differential expressed proteins. Of these, 54 were upregulated, and 44 were downregulated. Further analysis of the DEPs via STRING database showed that these changes primarily affect pathways linked to RNA processing, plasma membrane repair, and cytoskeleton organization. Indeed, we find the effects of E4 extend beyond proteins considered central to AD pathology. Knowing more about the protein interactions regulated by ApoE, in an isoform-specific manner, can reveal new mechanistic insights into development of AD.