PTEN downregulates p75NTR expression by decreasing DNA-binding activity of Sp1

p75NTR is expressed throughout the nervous system and its dysregulation is associated with pathological conditions. We have recently demonstrated a signalling cascade initiated by laminin (LN), which upregulates PTEN and downregulates p75NTR. Here we investigate the mechanism by which PTEN modulates p75NTR. Studies using PTEN mutants show that its protein phosphatase activity directly modulates p75NTR protein expression. Nuclear relocalization of PTEN subsequent to LN stimulation suggests transcriptional control of p75NTR expression, which was confirmed following EMSA and ChIP analysis of Sp1 transcription factor binding activity. LN and PTEN independently decrease the DNA-binding ability of PTEN to the p75NTR promoter. Sp1 regulation of p75NTR occurs via dephosphorylation of Sp1, thus reducing p75NTR transcription and protein expression. This mechanism represents a novel regulatory pathway which controls the expression level of a receptor with broad implications not only for the development of the nervous system but also for progression of pathological conditions.