Bidirectional Ca²⁺ signaling occurs between the endoplasmic reticulum and acidic organelles.

Journal article

The endoplasmic reticulum (ER) and acidic organelles (endo-lysosomes) act as separate Ca(2+) stores that release Ca(2+) in response to the second messengers IP3 and cADPR (ER) or NAADP (acidic organelles). Typically, trigger Ca(2+) released from acidic organelles by NAADP subsequently recruits IP3 or ryanodine receptors on the ER, an anterograde signal important for amplification and Ca(2+) oscillations/waves. We therefore investigated whether the ER can signal back to acidic organelles, using organelle pH as a reporter of NAADP action. We show that Ca(2+) released from the ER can activate the NAADP pathway in two ways: first, by stimulating Ca(2+)-dependent NAADP synthesis; second, by activating NAADP-regulated channels. Moreover, the differential effects of EGTA and BAPTA (slow and fast Ca(2+) chelators, respectively) suggest that the acidic organelles are preferentially activated by local microdomains of high Ca(2+) at junctions between the ER and acidic organelles. Bidirectional organelle communication may have wider implications for endo-lysosomal function as well as the generation of Ca(2+) oscillations and waves.

Authors: Morgan, A; Davis, L; Wagner, S; Lewis, A; Parrington, J

• Publication status: Published
• Journal: Journal of cell biology
• Volume: 200
• Issue: 6
• Pages: 789-805
• Publication date: 2013-03-01
• DOI: 10.1083/jcb.201204078
• EISSN: 1540-8140
• ISSN: 0021-9525
• Language: English
• Keywords: Endosomes; Chelating Agents; Endoplasmic Reticulum; Calcium Signaling; Lysosomes; NADP; Calcium; Animals; Lytechinus; Egtazic Acid