TRPV1 expression and activity during retinoic acid-induced neuronal differentiation

The transient receptor potential vanilloid subtype 1 (TRPV1) is a Ca²⁺-permeable channel primarily expressed in dorsal root ganglion neurons. Besides its function in thermogenic nociception and neurogenic inflammation, TRPV1 is involved in cell migration, cytoskeleton re-organisation and in neuronal guidance. To explore the TRPV1 level and activity during conditions for neuronal maturation, TRPV1-expressing SHSY5Y neuroblastoma cells were differentiated into a neuronal phenotype using all-trans-retinoic acid (RA). We show that RA highly up-regulated the total and cell surface TRPV1 protein expression but the TRPV1 mRNA level was unaffected. The up-regulated receptors were localised to the cell bodies and the developed neurites. Furthermore, RA increased both the basal intracellular free Ca²⁺ concentration by 30% as well as the relative capsaicin-induced Ca²⁺ influx. The results show that TRPV1 protein expression increases during RA-induced differentiation in vitro, which generates an altered intracellular Ca²⁺ homeostasis.