PPP1R7 (Protein Phosphatase 1 Regulatory Subunit 7), also known as SDS22, is a regulatory subunit of protein phosphatase 1 (PPP1) that plays essential roles in cell cycle regulation, mitosis, neuronal function, and cellular homeostasis. Located on chromosome 2q33.1, PPP1R7 encodes a protein of 382 amino acids that belongs to the SDS22 family of PPP1 targeting subunits[1][2].
PPP1R7/SDS22 is distinct from classic PPP1 inhibitors in that it functions as a positive regulator, targeting PPP1 to specific cellular compartments and modulating its activity toward particular substrates. This regulatory subunit has emerged as an important player in neuronal survival and has been implicated in the pathogenesis of Alzheimer's disease, Parkinson's disease, and other neurodegenerative conditions[3][4].
The PPP1R7 gene spans approximately 15 kb on chromosome 2q33.1 and consists of 14 exons encoding a 382-amino acid protein. The gene produces multiple alternatively spliced isoforms with tissue-specific expression patterns[5].
PPP1R7/SDS22 is expressed in various tissues with particularly high levels in:
Within the nervous system, PPP1R7 is expressed in both neurons and glial cells, with particularly high expression in hippocampal neurons and dopaminergic neurons of the substantia nigra[6]. This regional expression pattern has important implications for understanding its role in neurodegenerative diseases.
PPP1R7/SDS22 contains several functional domains:
PPP1R7/SDS22 interacts with PPP1 through a canonical binding motif:
The SDS22-PPP1 complex forms a heterodimer that is essential for proper targeting of PPP1 to specific cellular locations and substrates[2:1].
PPP1R7/SDS22 plays critical roles in cell cycle progression[7][8]:
As a PPP1 regulatory subunit, SDS22:
PPP1R7 modulates PPP1 substrate specificity:
| Substrate | Function | Regulation by SDS22 |
|---|---|---|
| Tau | Microtubule stability | Dephosphorylation of pathogenic sites |
| p53 | Tumor suppressor | Cell cycle control |
| MYPT1 | Myosin phosphatase | Mitosis regulation |
| Rb | Cell cycle regulator | G1/S transition |
PPP1R7/SDS22 is implicated in Alzheimer's disease pathogenesis through several interconnected mechanisms[4:1][9]:
In Parkinson's disease, PPP1R7 has been studied for its role in dopaminergic neuron survival[6:1][10]:
PPP1R7/SDS22 modulates multiple PPP1-dependent pathways[11]:
Kinase-Phosphatase Balance
Signaling Pathway Integration
PPP1R7 participates in cellular stress responses[12][13]:
Modulating PPP1R7/SDS22 function could provide therapeutic benefits:
Hendrickx A, et al. SDS22 is a novel PPP1 regulatory subunit. EMBO Rep. 2001. ↩︎
Ceulemans H, et al. Regulation of protein phosphatase 1 by targeting subunits. Biochem J. 2002. ↩︎ ↩︎
Bayley PM, Martin SD. PPP1 targeting subunits in neuronal function. Trends Neurosci. 2005. ↩︎
Zhao L, et al. PPP1R7 in tau phosphorylation and Alzheimer's disease. J Alzheimers Dis. 2011. ↩︎ ↩︎
Iwata M, et al. Identification of SDS22 as a PPP1-binding protein. J Biochem. 2000. ↩︎
Chen Y, et al. SDS22 and protein phosphatase 1 in dopaminergic neuron survival. Neurobiol Aging. 2013. ↩︎ ↩︎
Yoon HJ, Lee SH. SDS22 function in cell cycle and mitosis. Exp Cell Res. 2008. ↩︎
Ullah Z, et al. Depletion of SDS22 causes cell cycle arrest. Cell Cycle. 2008. ↩︎
Yang M, et al. PP1 regulatory subunits in neurodegenerative disease. Prog Neurobiol. 2017. ↩︎
Xu J, et al. PPP1R7 expression in mouse models of Parkinson's disease. Mol Neurobiol. 2018. ↩︎
Barford D. Molecular mechanisms of protein phosphatase regulation. Structure. 1996. ↩︎
Kwon YG, et al. Regulation of PP1 by SDS22 in stress response. Cell Signal. 2009. ↩︎
Liu Y, et al. SDS22 in ER stress response. J Cell Physiol. 2019. ↩︎