Phase separation of an actin nucleator by junctional microtubules regulates epithelial function.

Liquid-liquid phase separation (LLPS) is involved in various dynamic biological phenomena. In epithelial cells, dynamic regulation of junctional actin filaments tethered to the apical junctional complex (AJC) is critical for maintaining internal homeostasis against external perturbations; however, the role of LLPS in this process remains unknown. Here, after identifying a multifunctional actin nucleator, cordon bleu (Cobl), as an AJC-enriched microtubule-associated protein, we conducted comprehensive in vitro and in vivo analyses. We found that apical microtubules promoted LLPS of Cobl at the AJC, and Cobl actin assembly activity increased upon LLPS. Thus, microtubules spatiotemporally regulated junctional actin assembly for epithelial morphogenesis and paracellular barriers. Collectively, these findings established that LLPS of the actin nucleator Cobl mediated dynamic microtubule-actin cross-talk in junctions, which fine-tuned the epithelial barrier.

Voltage-sensing phosphatase (Vsp) regulates endocytosis-dependent nutrient absorption in chordate enterocytes.

Voltage-sensing phosphatase (Vsp) is a unique membrane protein that translates membrane electrical activities into the changes of phosphoinositide profiles. Vsp orthologs from various species have been intensively investigated toward their biophysical properties, primarily using a heterologous expression system. In contrast, the physiological role of Vsp in native tissues remains largely unknown. Here we report that zebrafish Vsp (Dr-Vsp), encoded by tpte gene, is functionally expressed on the endomembranes of lysosome-rich enterocytes (LREs) that mediate dietary protein absorption via endocytosis in the zebrafish mid-intestine. Dr-Vsp-deficient LREs were remarkably defective in forming endosomal vacuoles after initial uptake of dextran and mCherry. Dr-Vsp-deficient zebrafish exhibited growth restriction and higher mortality during the critical period when zebrafish larvae rely primarily on exogenous feeding via intestinal absorption. Furthermore, our comparative study on marine invertebrate Ciona intestinalis Vsp (Ci-Vsp) revealed co-expression with endocytosis-associated genes in absorptive epithelial cells of the Ciona digestive tract, corresponding to zebrafish LREs. These findings signify a crucial role of Vsp in regulating endocytosis-dependent nutrient absorption in specialized enterocytes across animal species.

Anaplastic Thyroid Carcinoma Treated with Lenvatinib.

OBJECTIVE: We report a case of anaplastic thyroid carcinoma (ATC) with local recurrence and distant metastasis that responded very well to treatment with lenvatinib, a new molecular-targeted anticancer drug. CASE REPORT: A 91-year-old Japanese woman presented with a 5-month history of a painless mass in her left anterior neck. She had a past history of total thyroidectomy and neck dissection for papillary carcinoma of the thyroid. Here she underwent neck dissection, and the histopathological diagnosis was lymph node metastasis of papillary carcinoma with anaplastic transformation. Five months later, a cervical lymph node swelled up again. Computed tomography demonstrated an enhanced mass in the neck and multiple nodules in both lungs. Recurrent ATC with multiple lung metastases was diagnosed, and molecular-targeted therapy with lenvatinib was initiated. The neck tumor reduced in 1 week, and the pulmonary nodules became completely hollow within 1 month. However, we had to discontinue lenvatinib because of severe side effects including high blood pressure, hypocalcemia, and hypoalbuminemia. Soon after discontinuation, the side effects subsided, but the tumor rapidly regrew. The patient died of lymphangiosis carcinomatosa 6 days after discontinuation. CONCLUSION: Although recent advances in molecular-targeted therapy have provided powerful cancer therapy tools, the negative side of this therapy must be addressed.

Possible contribution of pannexin-1 to ATP release in human upper airway epithelia.

Pannexins are a family of transmembrane nonselective channel proteins that participate in the release of ATP into extracellular space. Previous studies have suggested that pannexin-1 (Panx1) may constitute a local autocrine/paracrine system via transmitter ATP in association with the purinergic P2X7 receptor. In this study, we investigate the expressions of Panx1 and P2X7 in human nasal mucosa, together with hypotonic stress-induced ATP release from this tissue. Twenty men and one woman ranging in age from 10 to 82 years with an average age of 44.2 ± 4.4 years participated in the study. Inferior turbinates were collected from patients with chronic hypertrophic rhinitis during endoscopic endonasal surgery. The expressions of Panx1 and P2X7 were examined by fluorescence immunohistochemistry and quantitative reverse transcription-polymerase chain reaction (qRT-PCR). We also examined hypotonic stress-induced ATP release from the turbinate mucosa and the effects of channel blockers in an ex vivo experiment. Substantial expressions of both proteins were observed in human nasal mucosa. The immunoreactivity for Panx1 was stronger than that for P2X7. The presence of the transcripts of Panx1 and P2X7 was also shown by qRT-PCR. Ten and 100 µmol/L carbenoxolone (a Panx1 channel blocker) significantly inhibited the ATP release from the nasal mucosa, but flufenamic acid (a connexin channel blocker) and gadolinium (a stretch-activated channel blocker) did not. These results indicate the coexistence of Panx1 and P2X7 in, and Panx1-dependent ATP release from, the human nasal mucosa, suggesting the possible participation of these molecules in the physiological functions of the upper airway.

Identification of pannexins in rat nasal mucosa.

Pannexins are a second family of gap-junction proteins in vertebrates, classified as pannexin-1, pannexin-2, and pannexin-3. Pannexin-1 is one of the candidates for channel-mediated ATP release into the extracellular space. In airway epithelia, ATP signaling modulates multiple cellular functions such as mucus/ion secretion and mucociliary clearance systems. However, the expression of pannexins in the upper airway has not been investigated. Nasal septal mucosae were collected from adult male Wistar rats aged 20-24 weeks. The expression of pannexin-1, pannexin-2, and pannexin-3 was examined by reverse transcription polymerase chain reaction (RT-PCR) and by whole-mount fluorescence immunohistochemistry. Transcripts for pannexin-1, pannexin-2, and pannexin-3 were detected in nasal septal mucosae of adult rats by RT-PCR. Distinct immunohistochemical fluorescence for pannexin-1 was observed in the epithelial layer, whereas there was no immunoreactivity for pannexin-2 or pannexin-3. This is the first article establishing the existence of pannexins (predominantly pannexin-1) in the upper airway, suggesting their possible participation in the physiological functions of ATP release and signaling in this tissue.