Protocadherin 9 (PCDH9)

Protocadherin 9 (PCDH9) is a calcium-dependent cell adhesion protein belonging to the protocadherin family within the cadherin superfamily. It is classified as a non-clustered protocadherin, specifically in the δ1 (delta-1) subfamily, and contains multiple extracellular cadherin domains and a single transmembrane region. PCDH9 is predominantly expressed in the nervous system, localizes to synaptic junctions, and is believed to be involved in the formation and maintenance of neural circuits as well as cell-cell adhesion processes in the brain. Functionally, it acts as a tumor suppressor in several cancers: loss or downregulation of PCDH9 correlates with higher tumor grade, poorer prognosis, and increased cell proliferation, migration, and epithelial–mesenchymal transition. Beyond oncogenesis, genetic variation in PCDH9 is linked to increased risk for major depressive disorder and other neurodevelopmental or neuropsychiatric conditions. In animal models, deficiency of Pcdh9 impacts positive emotional behaviors and synaptic structure, particularly in the hippocampus and basolateral amygdala. There are no known drugs that directly target PCDH9, and it is not considered a canonical therapeutic target such as a receptor or enzyme. However, its expression levels and genetic variants are of interest as potential biomarkers for some cancers and neuropsychiatric disorders.

Other names

protocadherin-9cadherin superfamily protein VR4-11PCDH9protocadherin 9