Identification of a delta isoform of preprotachykinin mRNA in human mononuclear phagocytes and lymphocytes.

We have characterized preprotachykinin (PPT-A) gene transcript splicing products and identified a fourth isoform of PPT-A mRNA transcript in human peripheral blood-isolated monocytes and PBL. Using RT-PCR, Southern blot analysis and nucleotide sequencing analysis, we have identified the four isoforms of PPT-A transcripts (alpha, beta, gamma and delta) in human peripheral blood-isolated monocytes and PBL. The delta-PPT transcript present in the immune cells lacks exons 4 and 6. The sequences of exons 3, 5 and 7 of delta-PPT transcript completely match those of beta-PPT transcript. The alpha-PPT and beta-PPT sequences in these cells are identical to those obtained by Tan and Too (GenBank accession number U37539) and Harmar et al. (Genbank accession number X54469), but differ by a single nucleotide from another entry by Chiwakata et al. (Genbank accession number M68906). In comparison to this latter sequence, there was a C-->T change at amino acid position 87 (CCT-->CTT) which may result in a Pro to Leu change. Identification of the new SP mRNA transcript in both human CNS and immune cells supports the concept of an important biological link between CNS and immune system.