Differential expression of the bone and the liver tissue non-specific alkaline phosphatase isoforms in brain tissues

Abstract

The enzyme tissue non-specific alkaline phosphatase (TNAP) belongs to the ectophosphatase family. It is present in large amounts in bone in which it plays a role in mineralization but little is known about its function in other tissues. Arguments are accumulating for its involvement in the brain, in particular in view of the neurological symptoms accompanying human TNAP deficiencies. We have previously shown, by histochemistry, alkaline phosphatase (AP) activity in monkey brain vessels and parenchyma in which AP exhibits specific patterns. Here, we clearly attribute this activity to TNAP expression rather than to other APs in primates (human and marmoset) and in rodents (rat and mouse). We have not found any brain-specific transcripts but our data demonstrate that neuronal and endothelial cells exclusively express the bone TNAP transcript in all species tested, except in mouse neurons in which liver TNAP transcripts have also been detected. Moreover, we highlight the developmental regulation of TNAP expression; this also acts during neuronal differentiation. Our study should help to characterize the regulation of the expression of this ectophosphatase in various cell types of the central nervous system.

Reduced striatal ecto-nucleotidase activity in schizophrenia patients supports the “adenosine hypothesis”

“…This activity was intense and completely abrogated with the AP inhibitor levamisole. Previous reports have demonstrated that AP activity in human brain is attributable to TNAP expression [39,40].…”

Biochemical and proteomic investigation of bovine nasal secretion

“…The tissue non-specific AP has also been reported to be present in brain tissue (Brun-Heath et al, 2011) and circulating B cells in human (Hossain and Jung, 2008). The assay of AP in serum has been used as a marker of liver function for several decades (McComb et al, 1979) though bone AP can contribute to the serum activity.…”

Vitamin B-6 Metabolism and Interactions with TNAP

“…Brunel et al (1969) and Zisapel and Levi (1980) independently isolated from bovine brain alkaline phosphatases which had little activity toward pyridoxal phosphate. Brun-Heath et al (2011) recently demonstrated that the alkaline phosphatase expressed in human neuronal and endothelial cells corresponds to the ALPL gene driven by the bone promoter. The interactions between alkaline phosphatase, pyridoxal phosphate, pH and inorganic phosphate are complex.…”