Ppp3ca (protein phosphatase 3, catalytic subunit, alpha isoform) is a calcium- and calmodulin-dependent serine/threonine protein phosphatase. It is an important signaling molecule in T cells, neurons, the heart, and kidneys.
The catalytic domain of Ppp3ca has been disrupted in this knockout allele. Although the composition and distribution of T cell subsets is normal in homozygous knockout mice, and in vitro responses to mitogenic stimulation are similar to those of wildtype, the animals generate defective antigen-specific T cell responses in vivo.
Hyperphosphorylated tau, the major component of the helical filaments of Alzheimer's disease, accumulates in the brains of homozygous animals. This accumulation occurs particularly in the mossy fibers of the hippocampus, which contain the highest level of calcineurin in the brains of wildtype mice. The mossy fibers exhibit abnormalities in their cytoskeleton and a lower neurofilament/microtubule ratio than those of wildtype animals. Other Ppp3ca-deficient strains have been shown to have deficits in learning and memory that may result in part from these changes.
The kidneys of homozygotes fail to develop. Postnatal maturation of the nephrogenic zone is defective. Glomeruli also fail to mature in the nephrogenic zone and lack mesangial cells. Cells fail to proliferate and show an increase in cell death in the nephrogenic zone. There is an increase in collagen deposition and serum creatinine levels are increased. Water channel AQP2 (aquaporin 2) is mislocalized in the kidney collecting duct.
Homozygous mice fail to thrive and most die between 2 and 4 weeks of age due to a salivary gland/early digestion defect. Powdered rodent chow suspended in 1.5% gelatin or PancreVed digestive enzymes (VEDCO, NDC: 50989-771-25) in peanut oil added to moistened chow pellets rescues knockout animals and enables them to survive to adulthood. Loss of protein results in impaired salivary gland vesicular protein trafficking downstream of the inositol triphosphate receptor.
