scholarly journals Rab7 regulates primary cilia disassembly through cilia excision

2019 ◽  
Vol 218 (12) ◽  
pp. 4030-4041 ◽  
Author(s):  
Guang Wang ◽  
Huai-Bin Hu ◽  
Yan Chang ◽  
Yan Huang ◽  
Zeng-Qing Song ◽  
...  
Keyword(s):  
Cell Surface ◽  
Cell Signaling ◽  
Primary Cilium ◽  
Actin Polymerization ◽  
Essential Role ◽  
Primary Cilia ◽  
Small Gtpase ◽  
Proliferating Cells ◽  
Dynamic Transitions

The primary cilium is a sensory organelle that protrudes from the cell surface. Primary cilia undergo dynamic transitions between assembly and disassembly to exert their function in cell signaling. In this study, we identify the small GTPase Rab7 as a novel regulator of cilia disassembly. Depletion of Rab7 potently induced spontaneous ciliogenesis in proliferating cells and promoted cilia elongation during quiescence. Moreover, Rab7 performs an essential role in cilia disassembly; knockdown of Rab7 blocked serum-induced ciliary resorption, and active Rab7 was required for this process. Further, we demonstrate that Rab7 depletion significantly suppresses cilia tip excision, referred to as cilia ectocytosis, which has been identified as required for cilia disassembly. Mechanically, the failure of F-actin polymerization at the site of excision of cilia tips caused suppression of cilia ectocytosis on Rab7 depletion. Overall, our results suggest a novel function for Rab7 in regulating cilia ectocytosis and cilia disassembly via control of intraciliary F-actin polymerization.

scholarly journals A Model for Primary Cilium Biogenesis by Polarized Epithelial Cells: Role of the Midbody Remnant and Associated Specialized Membranes

2021 ◽  
Vol 8 ◽  
Author(s):  
Leticia Labat-de-Hoz ◽  
Armando Rubio-Ramos ◽  
Javier Casares-Arias ◽  
Miguel Bernabé-Rubio ◽  
Isabel Correas ◽  
...  
Keyword(s):  
Cell Surface ◽  
Primary Cilium ◽  
Primary Cilia ◽  
Control Cell ◽  
Future Research ◽  
Alternative Route ◽  
Ciliary Membrane ◽  
Cilium Formation ◽  
Membrane Compartmentalization

Primary cilia are solitary, microtubule-based protrusions surrounded by a ciliary membrane equipped with selected receptors that orchestrate important signaling pathways that control cell growth, differentiation, development and homeostasis. Depending on the cell type, primary cilium assembly takes place intracellularly or at the cell surface. The intracellular route has been the focus of research on primary cilium biogenesis, whereas the route that occurs at the cell surface, which we call the “alternative” route, has been much less thoroughly characterized. In this review, based on recent experimental evidence, we present a model of primary ciliogenesis by the alternative route in which the remnant of the midbody generated upon cytokinesis acquires compact membranes, that are involved in compartmentalization of biological membranes. The midbody remnant delivers part of those membranes to the centrosome in order to assemble the ciliary membrane, thereby licensing primary cilium formation. The midbody remnant's involvement in primary cilium formation, the regulation of its inheritance by the ESCRT machinery, and the assembly of the ciliary membrane from the membranes originally associated with the remnant are discussed in the context of the literature concerning the ciliary membrane, the emerging roles of the midbody remnant, the regulation of cytokinesis, and the role of membrane compartmentalization. We also present a model of cilium emergence during evolution, and summarize the directions for future research.

scholarly journals Transient primary cilia mediate robust Hedgehog pathway-dependent cell cycle control

2019 ◽  
Author(s):  
Emily K. Ho ◽  
Anaïs E. Tsai ◽  
Tim Stearns
Keyword(s):  
Cell Cycle ◽  
Primary Cilium ◽  
Primary Cilia ◽  
Cell Cycle Control ◽  
Proliferating Cells ◽  
Pathway Activity ◽  
Cell Cycles ◽  
Medulloblastoma Cell Line ◽  
Multiple Cell ◽  
Hh Signaling

SummaryThe regulation of proliferation is one of the primary functions of Hedgehog (Hh) signaling in development. Transduction of Hh signaling requires the primary cilium, a microtubule-based organelle that is necessary for several steps in the pathway (Corbit et al., 2005; Huangfu and Anderson, 2005; Huangfu et al., 2003; Liu et al., 2005; Rohatgi et al., 2007). Many cells only build a primary cilium upon cell cycle arrest in G0. In those proliferating cells that do make a cilium, it is a transient organelle, being assembled in G1 and disassembled sometime after, although exactly when is not well-characterized (Ford et al., 2018; Pugacheva et al., 2007; Wang and Dynlacht, 2018). Thus the requirement for primary cilia presents a conundrum: how are proliferative signals conveyed through an organelle that is present for only part of the cell cycle? Here we investigate this question in a mouse medulloblastoma cell line, SMB55, that requires cilium-mediated Hh pathway activity for proliferation (Zhao et al., 2015). We show that SMB55 cells are often ciliated beyond G1 into S phase, and the presence of the cilium determines the periods of Hh pathway activity. Using live imaging over multiple cell cycles, we define two windows of opportunity for Hh pathway activity, either of which is sufficient to effect cell cycle entry. The first is in the ciliated phase of the previous cell cycle, and the second is in G1 of the cell cycle in which the decision is made. We propose that the ability of cells to integrate Hh pathway activity from more than one cell cycle imparts robustness on Hh pathway control of proliferation and may have implications for other Hh-mediated events in development.

scholarly journals Interaction of Pestiviral E1 and E2 Sequences in Dimer Formation and Intracellular Retention

2021 ◽  
Vol 22 (14) ◽  
pp. 7285
Author(s):  
Yu Mu ◽  
Birke Andrea Tews ◽  
Christine Luttermann ◽  
Gregor Meyers
Keyword(s):  
Life Cycle ◽  
Cell Surface ◽  
Double Mutant ◽  
Essential Role ◽  
Infectious Clone ◽  
Intracellular Localization ◽  
Dimer Formation ◽  
Covalent Linkage ◽  
Crucial Step ◽  
Retention Signal

Pestiviruses contain three envelope proteins: Erns, E1, and E2. Expression of HA-tagged E1 or mutants thereof showed that E1 forms homodimers and -trimers. C123 and, to a lesser extent, C171, affected the oligomerization of E1 with a double mutant C123S/C171S preventing oligomerization completely. E1 also establishes disulfide linked heterodimers with E2, which are crucial for the recovery of infectious viruses. Co-expression analyses with the HA-tagged E1 wt/E1 mutants and E2 wt/E2 mutants demonstrated that C123 in E1 and C295 in E2 are the critical sites for E1/E2 heterodimer formation. Introduction of mutations preventing E1/E2 heterodimer formation into the full-length infectious clone of BVDV CP7 prevented the recovery of infectious viruses, proving that C123 in E1 and C295 in E2 play an essential role in the BVDV life cycle, and further support the conclusion that heterodimer formation is the crucial step. Interestingly, we found that the retention signal of E1 is mandatory for intracellular localization of the heterodimer, so that absence of the E1 retention signal directs the heterodimer to the cell surface even though the E2 retention signal is still present. The covalent linkage between E1 and E2 plays an essential role for this process.

scholarly journals Mechanical stimulation promotes enthesis injury repair by mobilizing Prx1+ cells via ciliary TGF-β signaling

2021 ◽  
Author(s):  
Han Xiao ◽  
Tao Zhang ◽  
Chang Jun Li ◽  
Yong Cao ◽  
Lin Feng Wang ◽  
...  
Keyword(s):  
Cell Migration ◽  
Rotator Cuff ◽  
Single Cell ◽  
Mechanical Stimulation ◽  
Essential Role ◽  
Primary Cilia ◽  
Underlying Mechanism ◽  
Rna Sequence ◽  
Injury Repair ◽  
Tgf Β1

Proper mechanical stimulation can improve rotator cuff enthsis injury repair. However, the underlying mechanism of mechanical stimulation promoting injury repair is still unknown. In this study, we found that Prx1+ cell was essential for murine rotator cuff enthesis development identified by single-cell RNA sequence and involved in the injury repair. Proper mechanical stimulation could promote the migration of Prx1+ cells to enhance enthesis injury repair. Meantime, TGF-β signaling and primary cilia played an essential role in mediating mechanical stimulation signaling transmission. Proper mechanical stimulation enhanced the release of active TGF-β1 to promote migration of Prx1+ cells. Inhibition of TGF-β signaling eliminated the stimulatory effect of mechanical stimulation on Prx1+ cell migration and enthesis injury repair. In addition, knockdown of Pallidin to inhibit TGF-βR2 translocation to the primary cilia or deletion of IFT88 in Prx1+ cells also restrained the mechanics-induced Prx1+ cells migration. These findings suggested that mechanical stimulation could increase the release of active TGF-β1 and enhance the mobilization of Prx1+ cells to promote enthesis injury repair via ciliary TGF-β signaling.

scholarly journals The retromer complex regulates C. elegans development and mammalian ciliogenesis

2021 ◽  
Author(s):  
Shuwei Xie ◽  
Ellie Smith ◽  
Carter Dierlam ◽  
Danita Mathew ◽  
Angelina Davis ◽  
...  
Keyword(s):  
Potential Function ◽  
Primary Cilium ◽  
Mammalian Cells ◽  
Primary Cilia ◽  
Vulval Development ◽  
Sorting Nexin ◽  
Capping Protein ◽  
C Elegans ◽  
Retromer Complex ◽  
Mother Centriole

The mammalian retromer is comprised of subunits VPS26, VPS29 and VPS35, and a more loosely-associated sorting nexin (SNX) heterodimer. Despite known roles for the retromer in multiple trafficking events in yeast and mammalian cells, its role in development is poorly understood, and its potential function in primary ciliogenesis remains unknown. Using CRISPR-Cas9 editing, we demonstrated that vps-26 homozygous knockout C. elegans have reduced brood sizes and impaired vulval development, as well as decreased body length which has been linked to defects in primary ciliogenesis. Since many endocytic proteins are implicated in the generation of primary cilia, we addressed whether the retromer regulates ciliogenesis in mammalian cells. We observed VPS35 localized to the primary cilium, and depletion of VPS26, VPS35 or SNX1/SNX5 led to decreased ciliogenesis. Retromer also coimmunoprecipitated with the capping protein, CP110, and was required for its removal from the mother centriole. Herein, we characterize new roles for the retromer in C. elegans development and in the regulation of ciliogenesis in mammalian cells, and suggest a novel role for the retromer in CP110 removal from the mother centriole.

Reduction of oxidative stress during recovery accelerates normalization of primary cilia length that is altered after ischemic injury in murine kidneys

2013 ◽  
Vol 304 (10) ◽  
pp. F1283-F1294 ◽  
Author(s):  
Jee In Kim ◽  
Jinu Kim ◽  
Hee-Seong Jang ◽  
Mi Ra Noh ◽  
Joshua H. Lipschutz ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Reactive Oxygen Species ◽  
Primary Cilium ◽  
Primary Cilia ◽  
Mdck Cells ◽  
Reactive Oxygen ◽  
Renal Tubular Cell ◽  
Oxygen Species ◽  
Renal Tubular ◽  
Cilium Length

The primary cilium is a microtubule-based nonmotile organelle that extends from the surface of cells, including renal tubular cells. Here, we investigated the alteration of primary cilium length during epithelial cell injury and repair, following ischemia/reperfusion (I/R) insult, and the role of reactive oxygen species in this alteration. Thirty minutes of bilateral renal ischemia induced severe renal tubular cell damage and an increase of plasma creatinine (PCr) concentration. Between 8 and 16 days following the ischemia, the increased PCr returned to normal range, although without complete histological restoration. Compared with the primary cilium length in normal kidney tubule cells, the length was shortened 4 h and 1 day following ischemia, increased over normal 8 days after ischemia, and then returned to near normal 16 days following ischemia. In the urine of I/R-subjected mice, acetylated tubulin was detected. The cilium length of proliferating cells was shorter than that in nonproliferating cells. Mature cells had shorter cilia than differentiating cells. Treatment with Mn(III) tetrakis(1-methyl-4-pyridyl) porphyrin (MnTMPyP), an antioxidant, during the recovery of damaged kidneys accelerated normalization of cilia length concomitant with a decrease of oxidative stress and morphological recovery in the kidney. In the Madin-Darby canine kidney (MDCK) cells, H2O2 treatment caused released ciliary fragment into medium, and MnTMPyP inhibited the deciliation. The ERK inhibitor U0126 inhibited elongation of cilia in normal and MDCK cells recovering from H2O2 stress. Taken together, our results suggest that primary cilia length reflects cell proliferation and the length of primary cilium is regulated, at least, in part, by reactive oxygen species through ERK.

scholarly journals Tissue factor activation: is disulfide bond switching a regulatory mechanism?

Blood ◽  
2007 ◽  
Vol 110 (12) ◽  
pp. 3900-3908 ◽  
Author(s):  
Usha R. Pendurthi ◽  
Samit Ghosh ◽  
Samir K. Mandal ◽  
L. Vijaya Mohan Rao
Keyword(s):  
Cell Surface ◽  
Cell Signaling ◽  
Tissue Factor ◽  
Disulfide Bond ◽  
Annexin V ◽  
Disulfide Exchange ◽  
Anionic Phospholipids ◽  
Coagulant Activity ◽  
Novel Concept ◽  
Cysteine Thiols

AbstractA majority of tissue factor (TF) on cell surfaces exists in a cryptic form (ie, coagulation function inactive) but retains its functionality in cell signaling. Recent studies have suggested that cryptic TF contains unpaired cysteine thiols and that activation involves the formation of the disulfide bond Cys186-Cys 209 and that protein disulfide isomerase (PDI) regulates TF coagulant and signaling activities by targeting this disulfide bond. This study was carried out to investigate the validity of this novel concept. Although treatment of MDA 231 tumor cells, fibroblasts, and stimulated endothelial cells with the oxidizing agent HgCl2 markedly increased the cell-surface TF coagulant activity, the increase is associated with increased anionic phospholipids at the cell surface. Annexin V, which binds to anionic phospholipids, attenuated the increased TF coagulant activity. It is noteworthy that treatment of cells with reducing agents also increased the cell surface TF activity. No evidence was found for either detectable expression of PDI at the cell surface or association of TF with PDI. Furthermore, reduction of PDI with the gene silencing had no effect on either TF coagulant or cell signaling functions. Overall, the present data undermine the recently proposed hypothesis that PDI-mediated disulfide exchange plays a role in regulating TF procoagulant and cell signaling functions.

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