We hypothesize that the transcription factor neuron restrictive silencer factor (NRSF) is an important determinant of the expression of the preprotachykinin (PPTA) gene (encoding substance P and Neurokinin A) and arginine vasopressin (AVP) both in neuronal and nonneuronal cells. NRSF, a zinc finger repressor protein, binds the NRSE motif found in many neuronal specific genes at a variety of promoter locations. However, it is found in a similar location at the major transcriptional start site, within both PPTA and AVP peptide promoters. We have correlated modulation of NRSF activity with expression of AVP and PPTA in a variety of cell types, indicating the general mechanism by which this protein may regulate expression. Specifically, they are as follows:(1). Expression of NRSF dramatically represses PPTA promoter activity in reporter gene constructs in primary cultures of DRG neurons.(2). The PPTA promoter activity is regulated differentially in osteoarthritic compared to normal chondrocytes. This regulation correlates with the region containing the NRSE site.(3). We have correlated a splice variant of NRSF with the establishment and progression of small cell lung carcinoma (SCLC) and demonstrated that NRSF variants can directly affect the activity of the AVP promoter in reporter gene constructs. If the deregulated expression of peptides in these diseases point to the mechanism determining the pathology, then perhaps targeting protocols that correct this deregulation may also reverse the specific disease phenotypes. Our data would indicate that modulation of NRSF activity would be a target for such intervention.