Xuexin Zhang

Significance: Stromal-interacting molecule 1 (STIM1) proteins are essential for the function of store-operated Ca ²⁺ entry (SOCE). Using transcriptomics, metabolomics, imaging, and inducible smooth muscle–specific STIM1 knockout mice expressing genetically encoded Ca ²⁺ sensors, we reveal a crucial function of STIM1 in airway remodeling and airway hyperresponsiveness in asthma. STIM1-mediated Ca ²⁺ oscillations in airway smooth muscle (ASM) cells are critical for ASM remodeling through metabolic and transcriptional reprogramming and cytokine secretion, including IL-6. These effects are driven by Ca ²⁺ -dependent activation of the transcription factor isoform NFAT4 specifically in ASM. Our data provide evidence that ASM STIM1 and SOCE are central triggers of asthma manifestations and advocate for the future use of STIM1 as a molecular target in asthma therapy.

Protein kinase C (PKC)-ε is required for membrane addition during IgG-mediated phagocytosis, but its role in this process is ill defined. Here, we performed high-resolution imaging, which reveals that PKC-ε exits the Golgi and enters phagosomes on vesicles that then fuse. TNF and PKC-ε colocalize at the Golgi and on vesicles that enter the phagosome. Loss of PKC-ε and TNF delivery upon nocodazole treatment confirmed vesicular transport on microtubules. That TNF+ vesicles were not delivered in macrophages from PKC-ε null mice, or upon dissociation of the Golgi-associated pool of PKC-ε, implies that Golgi-tethered PKC-ε is a driver of Golgi-to-phagosome trafficking. Finally, we established that the regulatory domain of PKC-ε is sufficient for delivery of TNF+ vesicles to the phagosome. These studies reveal a novel role for PKC-ε in focal exocytosis – its regulatory domain drives Golgi-derived vesicles to the phagosome, whereas catalytic activity is required for their fusion. This is one of the first examples of a PKC requirement for vesicular trafficking and describes a novel function for a PKC regulatory domain. This article has an associated First Person interview with the first author of the paper.

Voltage-gated L-type Ca ²⁺ channel (Ca _v 1.2) blockers (LCCBs) are major drugs for treating hypertension, the preeminent risk factor for heart failure. Vascular smooth muscle cell (VSMC) remodeling is a pathological hallmark of chronic hypertension. VSMC remodeling is characterized by molecular rewiring of the cellular Ca ²⁺ signaling machinery, including down-regulation of Ca _v 1.2 channels and up-regulation of the endoplasmic reticulum (ER) stromal-interacting molecule (STIM) Ca ²⁺ sensor proteins and the plasma membrane ORAI Ca ²⁺ channels. STIM/ORAI proteins mediate store-operated Ca ²⁺ entry (SOCE) and drive fibro-proliferative gene programs during cardiovascular remodeling. SOCE is activated by agonists that induce depletion of ER Ca ²⁺ , causing STIM to activate ORAI. Here, we show that the three major classes of LCCBs activate STIM/ORAI-mediated Ca ²⁺ entry in VSMCs. LCCBs act on the STIM N terminus to cause STIM relocalization to junctions and subsequent ORAI activation in a Ca _v 1.2-independent and store depletion-independent manner. LCCB-induced promotion of VSMC remodeling requires STIM1, which is up-regulated in VSMCs from hypertensive rats. Epidemiology showed that LCCBs are more associated with heart failure than other antihypertensive drugs in patients. Our findings unravel a mechanism of LCCBs action on Ca ²⁺ signaling and demonstrate that LCCBs promote vascular remodeling through STIM-mediated activation of ORAI. Our data indicate caution against the use of LCCBs in elderly patients or patients with advanced hypertension and/or onset of cardiovascular remodeling, where levels of STIM and ORAI are elevated.