scholarly journals Rab27b Is Expressed in a Wide Range of Exocytic Cells and Involved in the Delivery of Secretory Granules Near the Plasma Membrane

2007 ◽  
Vol 18 (11) ◽  
pp. 4377-4386 ◽  
Author(s):  
Hiroshi Gomi ◽  
Kenichi Mori ◽  
Shigeyoshi Itohara ◽  
Tetsuro Izumi
Keyword(s):  
Plasma Membrane ◽  
Knockout Mice ◽  
Secretory Granules ◽  
Secretory Cells ◽  
Rab Proteins ◽  
Double Knockout ◽  
Surface Protection ◽  
Complex Processes ◽  
Wide Range ◽  
Targeting Vector

Rab proteins regulate multiple, complex processes of membrane traffic. Among these proteins, Rab27a has been shown to function specifically in regulated exocytic pathways. However, the roles of Rab27b, another Rab27 subfamily member, have not been well characterized. We disrupted the Rab27b gene in mice. The targeting vector was designed to insert LacZ downstream of the initiation codon of the Rab27b gene so that the authentic promoter should drive this reporter gene. A comprehensive analysis of Rab27b expression using this mouse strain indicated that it is widely expressed not only in canonical secretory cells, but also in neurons and cells involved in surface protection and mechanical extension. To evaluate the function in pituitary endocrine cells where the isoform Rab27a is coexpressed, we generated Rab27a/Rab27b double knockout mice by crossing Rab27b knockout mice with Rab27a-mutated ashen mice. The polarized distribution of secretory granules close to the plasma membrane was markedly impaired in the pituitary of double knockout mice, indicating that the Rab27 subfamily is involved in the delivery of granules near the exocytic site. In conjunction with a phenotype having a pituitary devoid of the Rab27 effector granuphilin, we discuss the relationship between the residence and the releasable pool of granules.

Barrier role of actin filaments in regulated mucin secretion from airway goblet cells

2005 ◽  
Vol 288 (1) ◽  
pp. C46-C56 ◽  
Author(s):  
Camille Ehre ◽  
Andrea H. Rossi ◽  
Lubna H. Abdullah ◽  
Kathleen De Pestel ◽  
Sandra Hill ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Actin Filaments ◽  
Fluorescent Protein ◽  
Secretory Granules ◽  
Yellow Fluorescent Protein ◽  
Goblet Cells ◽  
Actin Binding ◽  
Secretory Cells ◽  
Cortical Actin ◽  
Mucin Secretion

Airway goblet cells secrete mucin onto mucosal surfaces under the regulation of an apical, phospholipase C/Gq-coupled P2Y2receptor. We tested whether cortical actin filaments negatively regulate exocytosis in goblet cells by forming a barrier between secretory granules and plasma membrane docking sites as postulated for other secretory cells. Immunostaining of human lung tissues and SPOC1 cells (an epithelial, mucin-secreting cell line) revealed an apical distribution of β- and γ-actin in ciliated and goblet cells. In goblet cells, actin appeared as a prominent subplasmalemmal sheet lying between granules and the apical membrane, and it disappeared from SPOC1 cells activated by purinergic agonist. Disruption of actin filaments with latrunculin A stimulated SPOC1 cell mucin secretion under basal and agonist-activated conditions, whereas stabilization with jasplakinolide or overexpression of β- or γ-actin conjugated to yellow fluorescent protein (YFP) inhibited secretion. Myristoylated alanine-rich C kinase substrate, a PKC-activated actin-plasma membrane tethering protein, was phosphorylated after agonist stimulation, suggesting a translocation to the cytosol. Scinderin (or adseverin), a Ca2+-activated actin filament severing and capping protein was cloned from human airway and SPOC1 cells, and synthetic peptides corresponding to its actin-binding domains inhibited mucin secretion. We conclude that actin filaments negatively regulate mucin secretion basally in airway goblet cells and are dynamically remodeled in agonist-stimulated cells to promote exocytosis.

scholarly journals A novel function for Rab proteins during maturation of secretory granules

2021 ◽  
Author(s):  
Sarah D Neuman ◽  
Annika R Lee ◽  
Jane E Selegue ◽  
Amy T Cavanagh ◽  
Arash Bashirullah
Keyword(s):  
Salivary Glands ◽  
Secretory Granule ◽  
Secretory Granules ◽  
Secretory Cells ◽  
Rab Proteins ◽  
Dependent Manner ◽  
Rab Gtpases ◽  
Cargo Proteins ◽  
Granule Maturation ◽  
Granule Growth

Regulated exocytosis is an essential process whereby professional secretory cells synthesize and secrete specific cargo proteins in a stimulus-dependent manner. Cargo-containing secretory granules are synthesized in the trans-Golgi Network (TGN); after budding from the TGN, granules undergo many modifications, including a dramatic increase in size. These changes occur during a poorly understood process called secretory granule maturation. Here we leverage the professional secretory cells of the Drosophila larval salivary glands as a model system to characterize a novel and unexpected role for Rab GTPases during secretory granule maturation. We find that secretory granules in the larval salivary glands increase in size ~300-fold between biogenesis and release, and loss of Rab1 or Rab11 dramatically reduces granule size. Surprisingly, we find that Rab1 and Rab11 protein localize to secretory granule membranes. Rab11 associates with granule membranes throughout the maturation process, and Rab11 is required for recruitment of Rab1. In turn, Rab1 associates specifically with immature secretory granules and drives granule growth. In addition to their roles in granule growth, both Rab1 and Rab11 appear to have additional roles during exocytosis; Rab11 function is necessary for exocytosis, while the presence of Rab1 on immature granules may prevent precocious exocytosis. Overall, these results highlight a new and unexpected role for Rab GTPases in secretory granule maturation.

scholarly journals The Rab27a effector exophilin7 promotes fusion of secretory granules that have not been docked to the plasma membrane

2013 ◽  
Vol 24 (3) ◽  
pp. 319-330 ◽  
Author(s):  
Hao Wang ◽  
Ray Ishizaki ◽  
Jun Xu ◽  
Kazuo Kasai ◽  
Eri Kobayashi ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Knockout Mice ◽  
Secretory Granules ◽  
Small Gtpase ◽  
Membrane Phospholipids ◽  
Β Cells ◽  
Β Cell ◽  
Pancreatic Β Cells ◽  
Insulin Granules ◽  
Insulin Exocytosis

Granuphilin, an effector of the small GTPase Rab27a, mediates the stable attachment (docking) of insulin granules to the plasma membrane and inhibits subsequent fusion of docked granules, possibly through interaction with a fusion-inhibitory Munc18-1/syntaxin complex. However, phenotypes of insulin exocytosis differ considerably between Rab27a- and granuphilin-deficient pancreatic β cells, suggesting that other Rab27a effectors function in those cells. We found that one of the putative Rab27a effector family proteins, exophilin7/JFC1/Slp1, is expressed in β cells; however, unlike granuphilin, exophilin7 overexpressed in the β-cell line MIN6 failed to show granule-docking or fusion-inhibitory activity. Furthermore, exophilin7 has no affinities to either Munc18-1 or Munc18-1–interacting syntaxin-1a, in contrast to granuphilin. Although β cells of exophilin7-knockout mice show no apparent abnormalities in intracellular distribution or in ordinary glucose-induced exocytosis of insulin granules, they do show impaired fusion in response to some stronger stimuli, specifically from granules that have not been docked to the plasma membrane. Exophilin7 appears to mediate the fusion of undocked granules through the affinity of its C2A domain toward the plasma membrane phospholipids. These findings indicate that the two Rab27a effectors, granuphilin and exophilin7, differentially regulate the exocytosis of either stably or minimally docked granules, respectively.

Abstract 468: The Dopamine D 1 -like Receptors Negatively Regulate the Expression and Function of the a 1 A Adrenergic Receptor

Hypertension ◽  
2013 ◽  
Vol 62 (suppl_1) ◽  
Author(s):  
Riley C Ennis ◽  
Van Anthony M Villar ◽  
Laureano D Asico ◽  
Crisanto S Escano ◽  
Jun B Feranil ◽  
...  
Keyword(s):  
Body Weight ◽  
Plasma Membrane ◽  
Knockout Mice ◽  
Adrenergic Receptor ◽  
Human Kidney ◽  
Proximal Tubules ◽  
Mouse Strains ◽  
Double Knockout ◽  
R And D ◽  
And Function

The homeostatic control of blood pressure hinges upon the delicate balance between pro-hypertensinogenic (e.g., sympathetic nervous system) and anti-hypertensinogenic systems (e.g., dopamine system). The D 1 -like dopamine receptors (D 1 R and D 5 R) and the α 1A adrenergic receptor (ARα 1A ) are endogenously expressed in the renal proximal tubules and engender opposing effects on sodium transport, i.e., natriuresis (D 1 R and D 5 R) or anti-natriuresis (ARα 1A ). We tested the hypothesis that the D 1 R and D 5 R interact with and regulate the ARα 1A in human renal proximal tubule cells (hRPTCs) and in mice. We found that the D 1 R and D 5 R colocalized with the ARα 1A in hRPTCs and in proximal tubules in human kidney sections. Both receptors immunoprecipitated, pulled-down, and co-fractionated with ARα 1A in lipid rafts. Short-term co-treatment with fenoldopam (1 μM, 15 min) reversed the ARα 1 agonist phenylephrine (10 μM, 15 min)-induced Na + ,K + -ATPase (NKA) translocation from the cytosol to the plasma membrane in hRPTCs (plasma membrane NKA: vehicle=100±5% vs. fenoldopam=65±3% vs. phenylephrine=177±5% vs. co-treatment=115±7%; P<0.05, n=3-4). Long-term fenoldopam (1 μM, 24 hr) treatment resulted in decreased D 1 R (70.0±5.9%, P<0.05, n=3) and D 5 R (50.1±10.7%, P<0.05, n=3), consistent with D 1 -like receptor desensitization, but increased ARα 1A abundance (142.6±4.3%, P<0.05, n=3) in hRPTCs. RNAi silencing of ARα 1A (48 hr) increased the expression of D 1 R and D 5 R. To determine the extent of regulation of each D 1 -like receptor on ARα 1A , we used the subclass-selective ARα 1 agonist phenylephrine (5 μg/kg body weight, i.p.) and the receptor-specific ARα 1A agonist A610603 (25 ng/kg body weight, i.p.) to inhibit Na + excretion in three mouse strains. Phenylephrine treatment resulted in 59.6%, 84.2%, 99.3%, and 99.5% reduction from basal level of 24-hr Na + excretion_while A61603 treatment resulted in 42.4%, 67.1%, 99.9%, and 100% reduction_in wild-type controls, D 1 R -/- , and D 5 R -/- knockout mice, and D 1 R/D 5 R -/- double knockout mice, respectively, suggesting a stronger regulatory effect of D 5 R on ARα 1A . Elucidating the intricacies of the interaction among these receptors is crucial for a better understanding of the crosstalk between anti- and pro-hypertensive systems.

Synaptotagmin (Syt) IX is an essential determinant for protein sorting to secretory granules in mast cells

Blood ◽  
2006 ◽  
Vol 109 (8) ◽  
pp. 3385-3392 ◽  
Author(s):  
Yael Haberman ◽  
Idit Ziv ◽  
Yaara Gorzalczany ◽  
Koret Hirschberg ◽  
Leonide Mittleman ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Mast Cells ◽  
Secretory Granules ◽  
Protein Sorting ◽  
Small Gtpase ◽  
Secretory Cells ◽  
Clathrin Adaptor ◽  
Lysosome Related Organelles ◽  
Golgi Network ◽  
Basophilic Leukemia

Abstract The secretory granules (SGs) of secretory cells of the hematopoietic lineage, such as the mast cells, are lysosome-related organelles whose membrane proteins travel through the plasma membrane and the endocytic system. Therefore, a mechanism must exist to prevent proteins destined to recycling or to the trans-Golgi network (TGN) from reaching the SGs. We now show that synaptotagmin (Syt) IX, a Syt homologue that is required for recycling from the endocytic recycling compartment (ERC) in rat basophilic leukemia (RBL-2H3) cultured mast cells, is involved in segregating recycling proteins from the SGs. By using as a marker the recycling protein TGN38, which cycles between the TGN, plasma membrane, and the ERC, we show that knock-down of Syt IX results in mistargeting of HA-tagged TGN38 to the SGs. We further demonstrate that Syt IX binds directly the small GTPase ARF1 and associates with the clathrin adaptor complex AP-1. These results therefore implicate Syt IX as an essential factor for the correct sorting of SGs proteins. Moreover, they place Syt IX as part of the machinery that is involved in the formation of transport carriers that mediate SGs protein sorting.

scholarly journals Weibel Palade Bodies: Unique Secretory Organelles of Endothelial Cells that Control Blood Vessel Homeostasis

2021 ◽  
Vol 9 ◽  
Author(s):  
Johannes Naß ◽  
Julian Terglane ◽  
Volker Gerke
Keyword(s):  
Endothelial Cells ◽  
Blood Flow ◽  
Plasma Membrane ◽  
Blood Vessel ◽  
Blood Cells ◽  
Secretory Granules ◽  
Von Willebrand Disease ◽  
Rab Proteins ◽  
Membrane Tethering ◽  
Von Willebrand

Vascular endothelial cells produce and release compounds regulating vascular tone, blood vessel growth and differentiation, plasma composition, coagulation and fibrinolysis, and also engage in interactions with blood cells thereby controlling hemostasis and acute inflammatory reactions. These interactions have to be tightly regulated to guarantee smooth blood flow in normal physiology, but also allow specific and often local responses to blood vessel injury and infectious or inflammatory insults. To cope with these challenges, endothelial cells have the remarkable capability of rapidly changing their surface properties from non-adhesive (supporting unrestricted blood flow) to adhesive (capturing circulating blood cells). This is brought about by the evoked secretion of major adhesion receptors for platelets (von-Willebrand factor, VWF) and leukocytes (P-selectin) which are stored in a ready-to-be-used form in specialized secretory granules, the Weibel-Palade bodies (WPB). WPB are unique, lysosome related organelles that form at the trans-Golgi network and further mature by receiving material from the endolysosomal system. Failure to produce correctly matured VWF and release it through regulated WPB exocytosis results in pathologies, most importantly von-Willebrand disease, the most common inherited blood clotting disorder. The biogenesis of WPB, their intracellular motility and their fusion with the plasma membrane are regulated by a complex interplay of proteins and lipids, involving Rab proteins and their effectors, cytoskeletal components as well as membrane tethering and fusion machineries. This review will discuss aspects of WPB biogenesis, trafficking and exocytosis focussing on recent findings describing factors contributing to WPB maturation, WPB-actin interactions and WPB-plasma membrane tethering and fusion.

scholarly journals The Mammalian Sec6/8 Complex Interacts with Ca2+ Signaling Complexes and Regulates Their Activity

2000 ◽  
Vol 150 (5) ◽  
pp. 1101-1112 ◽  
Author(s):  
Dong Min Shin ◽  
Xiao-Song Zhao ◽  
Weizhong Zeng ◽  
Marina Mozhayeva ◽  
Shmuel Muallem
Keyword(s):  
Plasma Membrane ◽  
Actin Cytoskeleton ◽  
Secretory Granules ◽  
Pancreatic Acinar Cell ◽  
Pancreatic Acinar Cells ◽  
Secretory Cells ◽  
Signaling Proteins ◽  
Intact Cells ◽  
Cell Extracts ◽  
Type 3

The localization of various Ca2+ transport and signaling proteins in secretory cells is highly restricted, resulting in polarized agonist-stimulated Ca2+ waves. In the present work, we examined the possible roles of the Sec6/8 complex or the exocyst in polarized Ca2+ signaling in pancreatic acinar cells. Immunolocalization by confocal microscopy showed that the Sec6/8 complex is excluded from tight junctions and secretory granules in these cells. The Sec6/8 complex was found in at least two cellular compartments, part of the complex showed similar, but not identical, localization with the Golgi apparatus and part of the complex associated with Ca2+ signaling proteins next to the plasma membrane at the apical pole. Accordingly, immunoprecipitation (IP) of Sec8 did not coimmunoprecipitate βCOP, Golgi 58K protein, or mannosidase II, all Golgi-resident proteins. By contrast, IP of Sec8 coimmunoprecipitates Sec6, type 3 inositol 1,4,5-trisphosphate receptors (IP3R3), and the Gβγ subunit of G proteins from pancreatic acinar cell extracts. Furthermore, the anti-Sec8 antibodies coimmunoprecipitate actin, Sec6, the plasma membrane Ca2+ pump, the G protein subunits Gαq and Gβγ, the β1 isoform of phospholipase C, and the ER resident IP3R1 from brain microsomal extracts. Antibodies against the various signaling and Ca2+ transport proteins coimmunoprecipitate Sec8 and the other signaling proteins. Dissociation of actin filaments in the immunoprecipitate had no effect on the interaction between Sec6 and Sec8, but released the actin and dissociated the interaction between the Sec6/8 complex and Ca2+ signaling proteins. Hence, the interaction between the Sec6/8 and Ca2+ signaling complexes is likely mediated by the actin cytoskeleton. The anti-Sec6 and anti-Sec8 antibodies inhibited Ca2+ signaling at a step upstream of Ca2+ release by IP3. Disruption of the actin cytoskeleton with latrunculin B in intact cells resulted in partial translocation of Sec6 and Sec8 from membranes to the cytosol and interfered with propagation of agonist-evoked Ca2+ waves. Our results suggest that the Sec6/8 complex has multiple roles in secretory cells including governing the polarized expression of Ca2+ signaling complexes and regulation of their activity.

Rab27 and its effectors in secretory granule exocytosis: a novel docking machinery composed of a Rab27·effector complex

2006 ◽  
Vol 34 (5) ◽  
pp. 691-695 ◽  
Author(s):  
M. Fukuda
Keyword(s):  
Plasma Membrane ◽  
Secretory Granule ◽  
Binding Proteins ◽  
Secretory Granules ◽  
Small Gtpase ◽  
Secretory Cells ◽  
Cell Type ◽  
Tissue Specific ◽  
C2 Domains ◽  
A Cell

A small GTPase Rab27 is present on secretory granules in a wide variety of secretory cells and on melanosomes in melanocytes, and it is involved in controlling the trafficking of these organelles through interaction with a cell-type- or tissue-specific Rab27 effector(s). Slps (synaptotagmin-like proteins) and rabphilin contain an N-terminal Rab27-binding domain and C-terminal tandem C2 domains, and some of the Rab27-binding proteins have recently been shown to promote docking of Rab27-bound organelles to the plasma membrane. This mini-review presents a model for how the Rab27·effector complex controls the docking step in the trafficking of Rab27-bound organelles. Our results indicate that Slp2-a, Slp4-a/granuphilin-a and rabphilin are capable of interacting with the plasma membrane directly or indirectly, and thus that these Rab27 effectors form a bridge between Rab27-bound organelles and the plasma membrane.

scholarly journals Sperm IZUMO1 Is Required for Binding Preceding Fusion With Oolemma in Mice and Rats

2022 ◽  
Vol 9 ◽  
Author(s):  
Takafumi Matsumura ◽  
Taichi Noda ◽  
Yuhkoh Satouh ◽  
Akane Morohoshi ◽  
Shunsuke Yuri ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Zona Pellucida ◽  
Knockout Mice ◽  
Knockout Mouse ◽  
Acrosome Reaction ◽  
Male Rats ◽  
Sperm Protein ◽  
Complex Processes ◽  
Sperm Binding ◽  
Mammalian Spermatozoa

Fertilization occurs as the culmination of multi-step complex processes. First, mammalian spermatozoa undergo the acrosome reaction to become fusion-competent. Then, the acrosome-reacted spermatozoa penetrate the zona pellucida and adhere to and finally fuse with the egg plasma membrane. IZUMO1 is the first sperm protein proven to be essential for sperm-egg fusion in mammals, as Izumo1 knockout mouse spermatozoa adhere to but fail to fuse with the oolemma. However, the IZUMO1 function in other species remains largely unknown. Here, we generated Izumo1 knockout rats by CRISPR/Cas9 and found the male rats were infertile. Unlike in mice, Izumo1 knockout rat spermatozoa failed to bind to the oolemma. Further investigation revealed that the acrosome-intact sperm binding conceals a decreased number of the acrosome-reacted sperm bound to the oolemma in Izumo1 knockout mice. Of note, we could not see any apparent defects in the binding of the acrosome-reacted sperm to the oolemma in the mice lacking recently found fusion-indispensable genes, Fimp, Sof1, Spaca6, or Tmem95. Collectively, our data suggest that IZUMO1 is required for the sperm-oolemma binding prior to fusion at least in rat.

scholarly journals Munc13-4 functions as a Ca2+ sensor for homotypic secretory granule fusion to generate endosomal exocytic vacuoles

2017 ◽  
Vol 28 (6) ◽  
pp. 792-808 ◽  
Author(s):  
Sang Su Woo ◽  
Declan J. James ◽  
Thomas F. J. Martin
Keyword(s):  
Plasma Membrane ◽  
Total Internal Reflection ◽  
Direct Evidence ◽  
Secretory Granules ◽  
Secretory Cells ◽  
Microscopy Imaging ◽  
C2 Domains ◽  
Protein Receptor ◽  
Compound Exocytosis ◽  
Sensitive Factor

Munc13-4 is a Ca2+-dependent SNARE (soluble N-ethylmaleimide–sensitive factor attachment protein receptor)- and phospholipid-binding protein that localizes to and primes secretory granules (SGs) for Ca2+-evoked secretion in various secretory cells. Studies in mast cell–like RBL-2H3 cells provide direct evidence that Munc13–4 with its two Ca2+-binding C2 domains functions as a Ca2+ sensor for SG exocytosis. Unexpectedly, Ca2+ stimulation also generated large (>2.4 μm in diameter) Munc13-4+/Rab7+/Rab11+ endosomal vacuoles. Vacuole generation involved the homotypic fusion of Munc13-4+/Rab7+ SGs, followed by a merge with Rab11+ endosomes, and depended on Ca2+ binding to Munc13-4. Munc13-4 promoted the Ca2+-stimulated fusion of VAMP8-containing liposomes with liposomes containing exocytic or endosomal Q-SNAREs and directly interacted with late endosomal SNARE complexes. Thus Munc13-4 is a tethering/priming factor and Ca2+ sensor for both heterotypic SG-plasma membrane and homotypic SG-SG fusion. Total internal reflection fluorescence microscopy imaging revealed that vacuoles were exocytic and mediated secretion of β-hexosaminidase and cytokines accompanied by Munc13-4 diffusion onto the plasma membrane. The results provide new molecular insights into the mechanism of multigranular compound exocytosis commonly observed in various secretory cells.

Sign in / Sign up

Export Citation Format

Share Document