A neuronal protein tyrosine phosphatase induced by nerve growth factor.

A new protein tyrosine phosphatase (PC12-PTP1) was identified in nerve growth factor (NGF)-treated PC12 cells. The mRNA level of PC12-PTP1 is increased 9-fold over the initial 8 h of NGF treatment and then decreases dramatically after 24 h of treatment. In rat brain, three transcripts corresponding to 1.5, 2.6, and 3.0 kilobases (kb) in size are detected by Northern blot analysis. Although the 1.5- and 2.6-kb transcripts are present in brain and other tissues, the 3-kb transcript is exclusively expressed in brain and the expression of this transcript alone increases following NGF treatment. PC12-PTP1 is a non-receptor protein tyrosine phosphatase (PTP) with a 50% sequence homology in the phosphatase domain with several other non-receptor PTPs. PC12-PTP1 fusion protein exhibits tyrosine phosphatase activity, and in vitro translation of the PC12-PTP1 transcript produces a major protein of 39 kDa. The data presented suggest that NGF regulates the expression of PC12-PTP1 during periods of neuronal growth and differentiation.