Kinetics of the thapsigargin-induced Ca mobilisation: A quantitative analysis in the HEK-293 cell line.

Thapsigargin (TG) inhibits the sarco/endoplasmic reticulum Ca ATPase (SERCA) pump and, when applied acutely, it initiates a Ca mobilisation that begins with the loss of Ca from the endoplasmic reticulum (ER) and culminates with store-operated Ca entry (SOCE) from the extracellular space. Using the popular model cell line HEK-293, we quantified TG-induced changes in cytosolic and ER Ca levels using FURA-2 and the FRET-based ER Ca sensor D1ER, respectively. Our analysis predicts an ER Ca leak of 5-6 µM⋅s for the typical basal ER Ca level of 335-407 µM in HEK-293 cells.

Bitter taste signaling in tracheal epithelial brush cells elicits innate immune responses to bacterial infection.

Constant exposure of the airways to inhaled pathogens requires efficient early immune responses protecting against infections. How bacteria on the epithelial surface are detected and first-line protective mechanisms are initiated are not well understood. We have recently shown that tracheal brush cells (BCs) express functional taste receptors.

Mycolactone enhances the Ca2+ leak from endoplasmic reticulum by trapping Sec61 translocons in a Ca2+ permeable state.

The Mycobacterium ulcerans exotoxin, mycolactone, is an inhibitor of co-translational translocation via the Sec61 complex. Mycolactone has previously been shown to bind to, and alter the structure of the major translocon subunit Sec61α, and change its interaction with ribosome nascent chain complexes. In addition to its function in protein translocation into the ER, Sec61 also plays a key role in cellular Ca2+ homeostasis, acting as a leak channel between the endoplasmic reticulum (ER) and cytosol.

Prolactin-sensitive olfactory sensory neurons regulate male preference in female mice by modulating responses to chemosensory cues.

Chemosensory cues detected in the nose need to be integrated with the hormonal status to trigger appropriate behaviors, but the neural circuits linking the olfactory and the endocrine system are insufficiently understood. Here, we characterize olfactory sensory neurons in the murine nose that respond to the pituitary hormone prolactin. Deletion of prolactin receptor in these cells results in impaired detection of social odors and blunts male preference in females.

Remodelling of Ca homeostasis is linked to enlarged endoplasmic reticulum in secretory cells.

The endoplasmic reticulum (ER) is extensively remodelled during the development of professional secretory cells to cope with high protein production. Since ER is the principal Ca store in the cell, we characterised the Ca homeostasis in NALM-6 and RPMI 8226 cells, which are commonly used as human pre-B and antibody secreting plasma cell models, respectively. Expression levels of Sec61 translocons and the corresponding Sec61-mediated Ca leak from ER, Ca storage capacity and store-operated Ca entry were significantly enlarged in the secretory RPMI 8226 cell line.

Eeyarestatin Compounds Selectively Enhance Sec61-Mediated Ca Leakage from the Endoplasmic Reticulum.

Eeyarestatin 1 (ES1) inhibits p97-dependent protein degradation, Sec61-dependent protein translocation into the endoplasmic reticulum (ER), and vesicular transport within the endomembrane system. Here, we show that ES1 impairs Ca homeostasis by enhancing the Ca leakage from mammalian ER. A comparison of various ES1 analogs suggested that the 5-nitrofuran (5-NF) ring of ES1 is crucial for this effect.