Hippocampal Cholinergic Neurostimulating Peptide Suppresses Acetylcholine Synthesis in T Lymphocytes

Lymphocytic cholinergic system has important roles in T cell functions, including immune responses and proliferation and differentiation of immune cells. T lymphocytes exclusively produces acetylcholine (ACh) via choline acetyltransferase (ChAT), activating their muscarinic and nicotinic ACh receptors (mAChRs and nAChRs, respectively) in an autocrine and paracrine manners. Hippocampal cholinergic neurostimulating peptide (HCNP) is an undecapeptide cleaved from N-terminal of phosphatidylethanolamine-binding protein 1 (PEBP1). HCNP enhances ACh synthesis through upreglation of ChAT expression in septo-hippocampal cholinergic neurons and participates in neuronal development and differentiation. Although PEBP1 and HCNP appears to be distributed ubiquitously in tissues and cells including spleen, its functions in immune cells have not been understood. In the present study, we observed that PEBP1 is also expressed in human and murine T cells. Long-term exposure to HCNP suppressed ChAT expression in MOLT3 human leukemic T cells, resulting in decreased release of ACh. HCNP also decreased the expression of extracellular signal-regulated kinase (ERK). Thus, HCNP appears to suppress lymphocytic cholinergic signaling, which might act as an immune modulator.