SNX27 regulates DRA activity and mediates its direct recycling by PDZ-interaction in early endosomes at the apical pole of Caco2 cells

SLC26 Anion Transporters

Solute carrier family 26 (SLC26) is a family of functionally diverse anion transporters found in all kingdoms of life. Anions transported by SLC26 proteins include chloride, bicarbonate, and sulfate, but also small organic dicarboxylates such as fumarate and oxalate. The human genome encodes ten functional homologs, several of which are causally associated with severe human diseases, highlighting their physiological importance. Here, we review novel insights into the structure and function of SLC26 proteins and summarize the physiological relevance of human members.

Emerging Role of Sorting Nexin 17 in Human Health and Disease

The distortion of the cellular membrane transport pathway has a profound impact on cell dynamics and can drive serious physiological consequences during the process of cell sorting. SNX17 is a member of the Sorting Nexin (SNX) family and plays a crucial role in protein sorting and transport in the endocytic pathway. SNX17, SNX27, and SNX31 belong to the SNX-FERM subfamily and possess the FERM domain, which can assist in endocytic transport and lysosomal degradation. The binding partners of SNX27 have been discovered to number over 100, and SNX27 has been linked to the development of Alzheimer's disease progression, tumorigenesis, cancer progression, and metastasis. However, the role and potential mechanisms of SNX17 in human health and disease remain poorly understood, and the function of SNX17 has not been fully elucidated. In this review, we summarize the structure and basic functions of SNX protein, focusing on providing current evidence of the role and possible mechanism of SNX17 in human neurodegenerative diseases and cardiovascular diseases.

The MYO1B and MYO5B motor proteins and the SNX27 sorting nexin regulate membrane mucin MUC17 trafficking in enterocytes

A dense glycocalyx, composed of the megaDalton-sized membrane mucin MUC17, coats the microvilli in the apical brush border of transporting intestinal epithelial cells, called enterocytes. The establishment of the MUC17-based glycocalyx in the mouse small intestine occurs at the critical suckling-weaning transition. The enterocytic glycocalyx extends 1 µm into the intestinal lumen and prevents the gut bacteria from directly attaching to the enterocytes. To date, the mechanism behind apical targeting of MUC17 to the brush border remains unknown. Here, we show that the actin-based motor proteins MYO1B and MYO5B, and the sorting nexin SNX27 regulate the intracellular trafficking of MUC17 in enterocytes. We demonstrate that MUC17 turnover at the brush border is slow and controlled by MYO1B and SNX27. Furthermore, we report that MYO1B regulates MUC17 protein levels in enterocytes, whereas MYO5B specifically governs MUC17 levels at the brush border. Together, our results extend our understanding of the intracellular trafficking of membrane mucins and provide mechanistic insights into how defective trafficking pathways render enterocytes sensitive to bacterial invasion.

Sorting nexins: role in the regulation of blood pressure

Sorting nexins (SNXs) are a family of proteins that regulate cellular cargo sorting and trafficking, maintain intracellular protein homeostasis, and participate in intracellular signaling. SNXs are also important in the regulation of blood pressure via several mechanisms. Aberrant expression and dysfunction of SNXs participate in the dysregulation of blood pressure. Genetic studies show a correlation between SNX gene variants and the response to antihypertensive drugs. In this review, we summarize the progress in SNX-mediated regulation of blood pressure, discuss the potential role of SNXs in the pathophysiology and treatment of hypertension, and propose novel strategies for the medical therapy of hypertension.

Endosomal Sorting Protein SNX27 and Its Emerging Roles in Human Cancers

SNX27 belongs to the sorting nexin (SNX) family of proteins that play a critical role in protein sorting and trafficking in the endocytosis pathway. This protein family is characterized by the presence of a Phox (PX) domain; however, SNX27 is unique in containing an additional PDZ domain. Recently, SNX27 has gained popularity as an important sorting protein that is associated with the retromer complex and mediates the recycling of internalized proteins from endosomes to the plasma membrane in a PDZ domain-dependent manner. Over 100 cell surface proteins have been identified as binding partners of the SNX27-retromer complex. However, the roles and underlying mechanisms governed by SNX27 in tumorigenesis remains to be poorly understood. Many of its known binding partners include several G-protein coupled receptors, such as β2-andrenergic receptor and parathyroid hormone receptor, are associated with multiple pathways implicated in oncogenic signaling and tumorigenesis. Additionally, SNX27 mediates the recycling of GLUT1 and the activation of mTORC1, both of which can regulate intracellular energy balance and promote cell survival and proliferation under conditions of nutrient deprivation. In this review, we summarize the structure and fundamental roles of SNX proteins, with a focus on SNX27, and provide the current evidence indicating towards the role of SNX27 in human cancers. We also discuss the gap in the field and future direction of SNX27 research. Insights into the emerging roles and mechanism of SNX27 in cancers will provide better development strategies to prevent and treat tumorigenesis.

Human epiblast lumenogenesis: From a cell aggregate to a lumenal cyst

The formation of a central lumen in the human epiblast is a critical step for development. However, because the lumen forms in the epiblast coincident with implantation, the molecular and cellular events of this early lumenogenesis process cannot be studied in vivo. Recent developments using new model systems have revealed insight into the underpinnings of epiblast formation. To provide an up-to-date comprehensive review of human epiblast lumenogenesis, we highlight recent findings from human and mouse models with an emphasis on new molecular understanding of a newly described apicosome compartment, a novel 'formative' state of pluripotency that coordinates with epiblast polarization, and new evidence about the physical and polarized trafficking mechanisms contributing to lumenogenesis.

Spatially resolved cell polarity proteomics of a human epiblast model

Critical early steps in human embryonic development include polarization of the inner cell mass, followed by formation of an expanded lumen that will become the epiblast cavity. Recently described three-dimensional (3D) human pluripotent stem cell-derived cyst (hPSC-cyst) structures can replicate these processes. To gain mechanistic insights into the poorly understood machinery involved in epiblast cavity formation, we interrogated the proteomes of apical and basolateral membrane territories in 3D human hPSC-cysts. APEX2-based proximity bioinylation, followed by quantitative mass spectrometry, revealed a variety of proteins without previous annotation to specific membrane subdomains. Functional experiments validated the requirement for several apically enriched proteins in cyst morphogenesis. In particular, we found a key role for the AP-1 clathrin adaptor complex in expanding the apical membrane domains during lumen establishment. These findings highlight the robust power of this proximity labeling approach for discovering novel regulators of epithelial morphogenesis in 3D stem cell-based models.