The p.E152K-STIM1 mutation deregulates Ca2+ signaling contributing to chronic pancreatitis

Abstract

Since deregulation of intracellular Ca2+ can lead to intracellular trypsin activation and STIM1 (stromal interaction molecule-1) protein is the main regulator of Ca2+ homeostasis in pancreatic acinar cells, we explored the Ca2+ signaling in 37 STIM1 variants found in three pancreatitis patient cohorts. Extensive functional analysis of one particular variant, p.E152K, identified in three patients, provided a plausible link between dysregulated Ca2+ signaling within pancreatic acinar cells and chronic pancreatitis susceptibility. Specifically, p.E152K, located within the STIM1 EF-hand and sterile α-motif domain, increased the release of Ca2+ from the endoplasmic reticulum in patient-derived fibroblasts and transfected HEK293T cells. This event was mediated by altered STIM1-sarco/endoplasmic reticulum calcium transport ATPase (SERCA) conformational change and enhanced SERCA pump activity leading to increased Store Operated Calcium Entry (SOCE). In the pancreatic AR42J cells expressing the p.E152K variant, Ca2+-signaling perturbations correlated with defects in trypsin activation and secretion, and increased cytotoxicity after cholecystokinin stimulation.

Functionally deficient TRPV6 variants contribute to hereditary and familial chronic pancreatitis

“…An important recent advance in pancreatitis genetics was the discovery of TRPV6 (encoding transient receptor potential cation channel subfamily V member 6; MIM# 606680) as a new CP susceptibility gene (Masamune et al, 2020; Sahin‐Tóth, 2020; Zou et al, 2020). Compared with other developments in the field of pancreatitis genetics over the last 10 years, which were either limited to specific populations or involved a small genetic effect (Burgos et al, 2021; Fjeld et al, 2015; Lasher et al, 2019; Moore et al, 2019; Rosendahl et al, 2018; Tang et al, 2018; Whitcomb et al, 2012; Witt et al, 2013; Wu et al, 2017; Zou et al, 2016), the TRPV6 discovery was noteworthy in that aggregated functionally deficient TRPV6 variants were found to exert a very strong genetic effect on CP across four populations; indeed, the corresponding odds ratios (OR) were 8.9 in the Chinese cohort (Zou et al, 2020), 48.3 in the Japanese cohort, and infinity in the French and German cohorts (Masamune et al, 2020). Unlike most other CP genes, TRPV6 is expressed in several types of epithelial cells, including pancreatic ductal and acinar cells, and encodes a constitutively active Ca 2+ ‐selective ion channel (Fecher‐Trost et al, 2017; Stoerger & Flockerzi, 2014).…”

Activation mechanisms and structural dynamics of STIM proteins

“…The close-by mutations S88G and G81N, which affect conserved residues and were identified upon whole exome sequencing of YPS patients, are likely pathogenic as well, as predicted by in silico analysis, but experimental studies are still awaited (Harris et al, 2017). Apart from the syndromes which are conventionally associated with STIM mutations and cancer, the STIM1 E152K mutant was identified by Burgos et al (2021) in three pancreatitis patients. The mutation was shown to promote Ca 2+ release from the ER in fibroblasts derived from patients and in the HEK293T expression system and an increase in SOCE.…”

“…Apart from the syndromes which are conventionally associated with STIM mutations and cancer, the STIM1 E152K mutant was identified by Burgos et al. (2021) in three pancreatitis patients. The mutation was shown to promote Ca 2+ release from the ER in fibroblasts derived from patients and in the HEK293T expression system and an increase in SOCE.…”