Store-operated calcium entry-activated autophagy protects EPC proliferation via the CAMKK2-MTOR pathway in ox-LDL exposure

Abstract

Improving biological functions of endothelial progenitor cells (EPCs) is beneficial to maintaining endothelium homeostasis and promoting vascular re-endothelialization. Because macroautophagy/ autophagy has been documented as a double-edged sword in cell functions, its effects on EPCs remain to be elucidated. This study was designed to explore the role and molecular mechanisms of store-operated calcium entry (SOCE)-activated autophagy in proliferation of EPCs under hypercholesterolemia. We employed oxidized low-density lipoprotein (ox-LDL) to mimic hypercholesterolemia in bone marrowderived EPCs from rat. Ox-LDL dose-dependently activated autophagy flux, while inhibiting EPC proliferation. Importantly, inhibition of autophagy either by silencing Atg7 or by 3-methyladenine treatment, further aggravated proliferative inhibition by ox-LDL, suggesting the protective effects of autophagy against ox-LDL. Interestingly, ox-LDL increased STIM1 expression and intracellular Ca 2C concentration. Either Ca 2C chelators or deficiency in STIM1 attenuated ox-LDL-induced autophagy activation, confirming the involvement of SOCE in the process. Furthermore, CAMKK2 (calcium/ calmodulin-dependent protein kinase kinase 2, b) activation and MTOR (mechanistic target of rapamycin [serine/threonine kinase]) deactivation were associated with autophagy modulation. Together, our results reveal a novel signaling pathway of SOCE-CAMKK2 in the regulation of autophagy and offer new insights into the important roles of autophagy in maintaining proliferation and promoting the survival capability of EPCs. This may be beneficial to improving EPC transplantation efficacy and enhancing vascular reendothelialization in patients with hypercholesterolemia.

Neuronal-targeted TFEB rescues dysfunction of the autophagy-lysosomal pathway and alleviates ischemic injury in permanent cerebral ischemia

“…As shown in Figure 4(c), in OGDtreated cortical neurons, the intracellular Ca 2+ level was significantly increased at the early stage of OGD, and returned to the basal level thereafter, which is consistent with a previous reports [46]. Furthermore, lines of evidence have indicated that intracellular Ca 2+ may regulate TFEB phosphorylation at least in part through the PPP3/calcineurin signaling pathways [47,48], especially in autophagy [29]. These data suggest the possibility that the intracellular Ca 2+ -dependent PPP3/calcineurin pathway may be an upstream regulator of TFEB function at the early stage of ischemia.…”

Inhibition of store-operated channels by carboxyamidotriazole sensitizes ovarian carcinoma cells to anti-BclxL strategies through Mcl-1 down-regulation

“…Nevertheless, in our conditions, P-Akt(308) was not down-regulated by CAI. Furthermore, since one of the major targets of CamKK2 is AMPK protein, it could be hypothesized that decreasing calcium could lead to a down-regulation in the CamKK2/AMPK pathway and consequently to an up-regulation of mTORC1, as previously described [ 69 , 70 ]. Nonetheless, the contrary result we obtained implies that calcium/CamKK2 is not the main pathway targeted by CAI and that CamKK2 is not involved in mTORC1 and Mcl-1 down-regulation.…”

<p>Ox-LDL Causes Endothelial Cell Injury Through ASK1/NLRP3-Mediated Inflammasome Activation via Endoplasmic Reticulum Stress</p>

“…Yang et al found that proliferation of endothelial progenitor cells can be inhibited obviously by ox-LDL at concentration 30-100 mg/L after 12 h exposure. [36][37][38][39][40] However, report also indicates that ox-LDL can enhance cell proliferation in human aortic smooth muscle cells or Endothelial cell at a relatively low concentration. [41][42][43][44] This difference might be due to cell performance differs to cell type when expose to ox-LDL.…”