Regulation of Intracellular Calcium by Endoplasmic Reticulum Proteins in Small Intestinal Interstitial Cells of Cajal

Chan Guk Park; Mei Jin Wu; Chansik Hong; Ju Yeon Jo; Han Yi Jiao; Hyun Park; Jae Yeoul Jun; Seok Choi

doi:10.5056/jnm16212

Regulation of Intracellular Calcium by Endoplasmic Reticulum Proteins in Small Intestinal Interstitial Cells of Cajal

J Neurogastroenterol Motil. 2018 Jan 30;24(1):128-137. doi: 10.5056/jnm16212.

Authors

Chan Guk Park¹, Mei Jin Wu², Chansik Hong², Ju Yeon Jo¹, Han Yi Jiao², Hyun Park³, Jae Yeoul Jun², Seok Choi²

Affiliations

¹ Department of Internal Medicine, College of Medicine, Chosun University, Gwangju, Korea.
² Department of Medicine, Graduate School, Chosun University, Gwangju, Korea.
³ Department of Physiology, College of Medicine, Chosun University, Gwangju, Korea.

Abstract

Background/aims: We investigated the role of representative endoplasmic reticulum proteins, stromal interaction molecule 1 (STIM1), and store-operated calcium entry-associated regulatory factor (SARAF) in pacemaker activity in cultured interstitial cells of Cajal (ICCs) isolated from mouse small intestine.

Methods: The whole-cell patch clamp technique applied for intracellular calcium ions ([Ca²⁺]_i) analysis with STIM1 or SARAF overexpressed cultured ICCs from mouse small intestine.

Results: In the current-clamping mode, cultured ICCs displayed spontaneous pacemaker potentials. External carbachol exposure produced tonic membrane depolarization in the current-clamp mode, which recovered within a few seconds into normal pacemaker potentials. In STIM1-overexpressing cultured ICCs pacemaker potential frequency was increased, and in SARAF-overexpressing ICCs pacemaker potential frequency was strongly inhibited. The application of gadolinium (a non-selective cation channel inhibitor) or a Ca²⁺-free solution to understand Orai channel involvement abolished the generation of pacemaker potentials. When recording intracellular Ca²⁺ concentration with Fluo 3-AM, STIM1-overexpressing ICCs showed an increased number of spontaneous intracellular Ca²⁺ oscillations. However, SARAF-overexpressing ICCs showed fewer spontaneous intracellular Ca²⁺ oscillations.

Conclusion: Endoplasmic reticulum proteins modulated the frequency of pacemaker activity in ICCs, and levels of STIM1 and SARAF may determine slow wave patterns in the gastrointestinal tract.

Keywords: Interstitial cells of Cajal; Intestinal motility; Store-operated calcium entry-associated regulatory factor; Stromal interaction molecule 1.