complex(p(HGNC:PPP2CB), p(HGNC:PPP2R1A), p(INTERPRO:"Protein phosphatase 2A regulatory subunit PR55"))

Components

• p(HGNC:PPP2R1A)
• p(INTERPRO:"Protein phosphatase 2A regulatory subunit PR55")
• p(HGNC:PPP2CB)

Notably, the loss of neuronal PP2A/Bα holoenzymes correlates with the down-regulation of PP2A methylation and severity of phosphorylated tau (P-tau) pathology in AD-affected brain regions (Sontag et al.,2004 a,b). PubMed:24653673

As described earlier, it is especially significant that the biogenesis of PP2A/Bα holoenzymes is intimately related to the methylation state of PP2A PubMed:24653673

The deregulation of PP2A methylation in AD is especially interesting, not only because it can lead to a loss of PP2A/Bα, a major tau regulator, but also because PP2A methylation state is intimately linked to the integrity of one-carbon metabolism, which regulates SAM supply (Reviewed in Fowler,2005). PubMed:24653673

This is potentially physiologically significant since phosphorylation of tau at Thr-231, a target site for ERK2, GSK3β, and cdk5, occurs early in AD and can further inhibit the ability of PP2A/Bα to dephosphorylate other major AD-tau phosphoepitopes (Landrieu et al.,2011). PubMed:24653673

Significantly, downregulation of LCMT1 expression leads to a significant decrease of PP2A methylation and concomitant loss of PP2A holoenzymes containing the regulatory Bα (or PPP2R2A) subunit (PP2A/Bα; Lee and Pallas,2007; Sontag et al.,2008; MacKay et al.,2013). PubMed:24653673

Conversely, decreased PP2A methylation and PP2A/Bα levels in AD will disrupt normal PP2A-tau interactions (Sontag et al., 2007), thereby preventing PP2A-mediated tau dephosphorylation while allowing for enhanced binding of Fyn kinase or other regulators to the tau proteins. PubMed:24653673

The deregulation of PP2A methylation in AD is especially interesting, not only because it can lead to a loss of PP2A/Bα, a major tau regulator, but also because PP2A methylation state is intimately linked to the integrity of one-carbon metabolism, which regulates SAM supply (Reviewed in Fowler,2005). PubMed:24653673

Notably, the loss of neuronal PP2A/Bα holoenzymes correlates with the down-regulation of PP2A methylation and severity of phosphorylated tau (P-tau) pathology in AD-affected brain regions (Sontag et al.,2004 a,b). PubMed:24653673

Of particular relevance to the Alzheimer’s disease (AD) field, PP2A/Bα holoenzymes can directly bind to the microtubule-associated protein tau (Sontag et al.,1999, 2012; Xu et al.,2008). PubMed:24653673

It is noteworthy that PP2A/Bα can directly bind to tau via a domain encompassing the microtubule-binding of tau; this interaction maximizes the efficiency of tau dephosphorylation by PP2A (Sontag et al.,1999; Xu et al.,2008; Figure 3A). PubMed:24653673

Conversely, decreased PP2A methylation and PP2A/Bα levels in AD will disrupt normal PP2A-tau interactions (Sontag et al., 2007), thereby preventing PP2A-mediated tau dephosphorylation while allowing for enhanced binding of Fyn kinase or other regulators to the tau proteins. PubMed:24653673

Notably, the loss of neuronal PP2A/Bα holoenzymes correlates with the down-regulation of PP2A methylation and severity of phosphorylated tau (P-tau) pathology in AD-affected brain regions (Sontag et al.,2004 a,b). PubMed:24653673

As described earlier, it is especially significant that the biogenesis of PP2A/Bα holoenzymes is intimately related to the methylation state of PP2A PubMed:24653673

The deregulation of PP2A methylation in AD is especially interesting, not only because it can lead to a loss of PP2A/Bα, a major tau regulator, but also because PP2A methylation state is intimately linked to the integrity of one-carbon metabolism, which regulates SAM supply (Reviewed in Fowler,2005). PubMed:24653673

Notably, the loss of neuronal PP2A/Bα holoenzymes correlates with the down-regulation of PP2A methylation and severity of phosphorylated tau (P-tau) pathology in AD-affected brain regions (Sontag et al.,2004 a,b). PubMed:24653673

While many PP2A holoenzymes have the potential to indirectly affect tau phosphorylation by modulating key tau protein kinases (For example see Louis et al., 2011), biochemical and structural studies have demonstrated that PP2A/Bα is the primary PP2A isoform that mediates tau dephosphorylation (Sontag et al.,1996, 1999; Xu et al.,2008). PubMed:24653673

Specific inhibition of PP2A/Bα is associated with enhanced tau phosphorylation at many AD-like phospho epitopes, and subsequent inability of tau to bind to and stabilize microtubules (Sontag et al., 1996). PubMed:24653673

Specific inhibition of PP2A/Bα is associated with enhanced tau phosphorylation at many AD-like phospho epitopes, and subsequent inability of tau to bind to and stabilize microtubules (Sontag et al., 1996). PubMed:24653673

Deregulation of PP2A/Bα alone also affects microtubule stability (Nunbhakdi-Craig et al., 2007) and neurite outgrowth (Sontag et al.,2010) in neuroblastoma cells PubMed:24653673

Deregulation of PP2A/Bα alone also affects microtubule stability (Nunbhakdi-Craig et al., 2007) and neurite outgrowth (Sontag et al.,2010) in neuroblastoma cells PubMed:24653673

Conversely, decreased PP2A methylation and PP2A/Bα levels in AD will disrupt normal PP2A-tau interactions (Sontag et al., 2007), thereby preventing PP2A-mediated tau dephosphorylation while allowing for enhanced binding of Fyn kinase or other regulators to the tau proteins. PubMed:24653673

The deregulation of PP2A methylation in AD is especially interesting, not only because it can lead to a loss of PP2A/Bα, a major tau regulator, but also because PP2A methylation state is intimately linked to the integrity of one-carbon metabolism, which regulates SAM supply (Reviewed in Fowler,2005). PubMed:24653673