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Published on: September 9, 2014
Full-length and truncated neurokinin-1 receptor expression and function during monocyte/macrophage differentiation
J-P Lai1, W Z Ho, L E Kilpatrick
1Division of Allergy and Immunology, The Joseph Stokes Jr. Research Institute, Children's Hospital of Philadelphia, and Department of Pediatrics, University of Pennsylvania Medical School, Philadelphia, PA 19104, USA.
Summary
Substance P receptor (NK-1R) exists in full-length and truncated forms. Macrophage differentiation induces full-length NK-1R, enabling SP-mediated calcium signaling, while truncated NK-1R primes CCL5 responses.
Area of Science:
- Immunology
- Cell Biology
- Neuroscience
Background:
- The neurokinin-1 receptor (NK-1R), which binds substance P (SP), has full-length (407 aa) and truncated (311 aa) forms differing in C-terminal length.
- Human monocyte/macrophage THP-1 cells offer a model to study NK-1R expression and function during differentiation.
Purpose of the Study:
- To investigate the differential expression and function of full-length and truncated NK-1R in undifferentiated versus PMA-differentiated THP-1 cells.
- To elucidate the distinct signaling pathways mediated by each NK-1R isoform.
Main Methods:
- Real-time PCR and immunofluorescence staining to assess NK-1R expression.
- Calcium imaging to measure SP-induced and CCL5-mediated intracellular calcium ([Ca2+]) increases.
- Functional studies using NK-1R antagonist aprepitant and plasmid transfection.
Main Results:
- Undifferentiated THP-1 cells exclusively expressed truncated NK-1R, showing SP priming of CCL5-induced [Ca2+] increase but no direct SP response.
- PMA-induced differentiation led to full-length NK-1R expression, enabling direct SP-induced [Ca2+] increase.
- Aprepitant inhibited SP-induced [Ca2+] in differentiated cells and SP priming in undifferentiated cells, confirming isoform-specific mediation.
Conclusions:
- NK-1R expression is dynamically regulated during THP-1 cell differentiation.
- Full-length NK-1R mediates direct SP responses, while truncated NK-1R modulates chemokine signaling.
- These findings highlight distinct roles for NK-1R isoforms in macrophage biology and neuro-immune interactions.
