Nicotinic acid adenine dinucleotide phosphate activates two-pore channel TPC1 to mediate lysosomal Ca2+ release in endothelial colony-forming cells

J Cell Physiol. 2021 Jan;236(1):688-705. doi: 10.1002/jcp.29896. Epub 2020 Jun 24.


Nicotinic acid adenine dinucleotide phosphate (NAADP) is the most recently discovered Ca2+ -releasing messenger that increases the intracellular Ca2+ concentration by mobilizing the lysosomal Ca2+ store through two-pore channels 1 (TPC1) and 2 (TPC2). NAADP-induced lysosomal Ca2+ release regulates multiple endothelial functions, including nitric oxide release and proliferation. A sizeable acidic Ca2+ pool endowed with TPC1 is also present in human endothelial colony-forming cells (ECFCs), which represent the only known truly endothelial precursors. Herein, we sought to explore the role of the lysosomal Ca2+ store and TPC1 in circulating ECFCs by harnessing Ca2+ imaging and molecular biology techniques. The lysosomotropic agent, Gly-Phe β-naphthylamide, and nigericin, which dissipates the proton gradient which drives Ca2+ sequestration by acidic organelles, caused endogenous Ca2+ release in the presence of a replete inositol-1,4,5-trisphosphate (InsP3 )-sensitive endoplasmic reticulum (ER) Ca2+ pool. Likewise, the amount of ER releasable Ca2+ was reduced by disrupting lysosomal Ca2+ content. Liposomal delivery of NAADP induced a transient Ca2+ signal that was abolished by disrupting the lysosomal Ca2+ store and by pharmacological and genetic blockade of TPC1. Pharmacological manipulation revealed that NAADP-induced Ca2+ release also required ER-embedded InsP3 receptors. Finally, NAADP-induced lysosomal Ca2+ release was found to trigger vascular endothelial growth factor-induced intracellular Ca2+ oscillations and proliferation, while it did not contribute to adenosine-5'-trisphosphate-induced Ca2+ signaling. These findings demonstrated that NAADP-induced TPC1-mediated Ca2+ release can selectively be recruited to induce the Ca2+ response to specific cues in circulating ECFCs.

Keywords: Ca2+ signaling; NAADP; VEGF; endothelial colony-forming cells; two-pore channel 1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium / metabolism
  • Calcium Channels / drug effects*
  • Calcium Channels / metabolism
  • Calcium Signaling / drug effects
  • Calcium Signaling / physiology
  • Cell Line
  • Endoplasmic Reticulum / drug effects*
  • Endoplasmic Reticulum / metabolism
  • Endothelial Cells / drug effects*
  • Endothelial Cells / metabolism
  • Humans
  • Lysosomes / drug effects
  • Lysosomes / metabolism
  • NADP / analogs & derivatives*
  • NADP / metabolism
  • NADP / pharmacology
  • Vascular Endothelial Growth Factor A / drug effects
  • Vascular Endothelial Growth Factor A / metabolism


  • Calcium Channels
  • Vascular Endothelial Growth Factor A
  • NADP
  • Calcium