scholarly journals Syntaxin 17 Is Abundant in Steroidogenic Cells and Implicated in Smooth Endoplasmic Reticulum Membrane Dynamics

2000 ◽  
Vol 11 (8) ◽  
pp. 2719-2731 ◽  
Author(s):  
Martin Steegmaier ◽  
Viola Oorschot ◽  
Judith Klumperman ◽  
Richard H. Scheller
Keyword(s):  
Endoplasmic Reticulum ◽  
Smooth Endoplasmic Reticulum ◽  
Regulatory Protein ◽  
Cell Types ◽  
Membrane Dynamics ◽  
Endoplasmic Reticulum Membrane ◽  
Steroidogenic Cell ◽  
Molecular Machinery ◽  
Intermediate Compartment ◽  
Steroidogenic Cells

The endoplasmic reticulum (ER) consists of subcompartments that have distinct protein constituents, morphological appearances, and functions. To understand the mechanisms that regulate the intricate and dynamic organization of the endoplasmic reticulum, it is important to identify and characterize the molecular machinery involved in the assembly and maintenance of the different subcompartments. Here we report that syntaxin 17 is abundantly expressed in steroidogenic cell types and specifically localizes to smooth membranes of the ER. By immunoprecipitation analyses, syntaxin 17 exists in complexes with a syntaxin regulatory protein, rsly1, and/or two intermediate compartment SNARE proteins, rsec22b and rbet1. Furthermore, we found that syntaxin 17 is anchored to the smooth endoplasmic reticulum through an unusual mechanism, requiring two adjacent hydrophobic domains near its carboxyl terminus. Converging lines of evidence indicate that syntaxin 17 functions in a vesicle-trafficking step to the smooth-surfaced tubular ER membranes that are abundant in steroidogenic cells.

Aids: Tubuloreticular Structures (Trs), Cylindrical Confronting Cisternae (Ccc), and Related Alterations

1999 ◽  
Vol 5 (S2) ◽  
pp. 1092-1093
Author(s):  
Gurdip S. Sidhu ◽  
Nicholas D. Cassai
Keyword(s):  
Endoplasmic Reticulum ◽  
Smooth Endoplasmic Reticulum ◽  
Matrix Material ◽  
Cell Types ◽  
Test Tube ◽  
Endoplasmic Reticulum Membrane ◽  
Annulate Lamellae ◽  
Electron Dense Material ◽  
Tubuloreticular Inclusions ◽  
Tubuloreticular Structures

TRS and CCC are endoplasmic reticulum membrane-derived structures seen in HIV-infected individuals in a variety of cell types. TRS (synonym: tubuloreticular inclusions) are 24-25 nm in diameter, branching tubules which are short or long and associated with the granular or smooth endoplasmic reticulum, the Golgi complex, the perinuclear cistern, and annulate lamellae (Fig. 1-3, 8). The tubules are noticeably more stretched out in Kaposi's sarcoma endothelial cells, presumably by an increase of matrix material within the reticulum sac (Fig. 3). TRS consist of membranous components, including polypeptides, but lack nucleic acid.CCC (test tube and ring-shaped forms; curvilinear membranes) are formed by a concentric stacking of two or three cisterns of endoplasmic reticulum resembling nuclear membrane in mitosis (Fig. 7), but with the interposition between the opposing membranes of a layer of electron-dense material that is resistant to lipid solvents (Fig. 4,5,8).

scholarly journals Establishment of a Human Nonluteinized Granulosa Cell Line that Transitions from the Gonadotropin-Independent to the Gonadotropin-Dependent Status

Endocrinology ◽  
2012 ◽  
Vol 153 (6) ◽  
pp. 2851-2860 ◽  
Author(s):  
Bayasula ◽  
Akira Iwase ◽  
Tohru Kiyono ◽  
Sachiko Takikawa ◽  
Maki Goto ◽  
...  
Keyword(s):  
Cell Line ◽  
Granulosa Cell ◽  
Granulosa Cells ◽  
Early Stage ◽  
Regulatory Protein ◽  
Cell Types ◽  
Mrna Levels ◽  
Steroidogenic Cell ◽  
Morphogenetic Protein ◽  
Steroidogenic Acute Regulatory

The ovary is a complex endocrine organ responsible for steroidogenesis and folliculogenesis. Follicles consist of oocytes and two primary steroidogenic cell types, the granulosa cells, and the theca cells. Immortalized human granulosa cells are essential for researching the mechanism of steroidogenesis and folliculogenesis. We obtained granulosa cells from a 35-yr-old female and immortalized them by lentivirus-mediated transfer of several genes so as to establish a human nonluteinized granulosa cell line (HGrC1). We subsequently characterized HGrC1 and investigated its steroidogenic performance. HGrC1 expressed enzymes related to steroidogenesis, such as steroidogenic acute regulatory protein, CYP11A, aromatase, and gonadotropin receptors. Stimulation with FSH increased the mRNA levels of aromatase, which consequently induced the aromatization of androstenedione to estradiol. Activin A increased the mRNA levels of the FSH receptor, which were synergistically up-regulated with FSH stimulation. HGrC1 also expressed a series of ligands and receptors belonging to the TGF-β superfamily. A Western blot analysis showed that bone morphogenetic protein (BMP)-4, BMP-6, and BMP-7 phosphorylated small mother against decapentaplegic (Smad)1/5/8, whereas growth differentiation factor-9 phosphorylated Smad2/3. BMP-15 and anti-Müllerian hormone phosphorylated Smad1/5/8 while also weakly phosphorylating Smad2/3. These results indicate that HGrC1 may possess the characteristics of granulosa cells belonging to follicles in the early stage. HGrC1 might also be capable of displaying the growth transition from a gonadotropin-independent status to gonadotropin-dependent one.

NSP-encoded reticulons, neuroendocrine proteins of a novel gene family associated with membranes of the endoplasmic reticulum

1994 ◽  
Vol 107 (9) ◽  
pp. 2403-2416 ◽  
Author(s):  
H.J. van de Velde ◽  
A.J. Roebroek ◽  
N.H. Senden ◽  
F.C. Ramaekers ◽  
W.J. Van de Ven
Keyword(s):  
Amino Acids ◽  
Endoplasmic Reticulum ◽  
Gene Family ◽  
Biochemical Characterization ◽  
Smooth Endoplasmic Reticulum ◽  
Dendritic Tree ◽  
Cell Types ◽  
In Vitro Translation ◽  
Amino Terminal

The novel NSP gene was previously shown to encode, among a variety of neuroendocrine cell types, two 3′-overlapping transcripts, a 3.4 kb one for NSP-A (776 amino acids) and a 1.8 kb one for NSP-C (208 amino acids). The deduced proteins, which were predicted to possess distinct amino-terminal regions, appeared to exhibit some architectural resemblance to known neuroendocrine proteins. In this paper the biochemical characterization and subcellular localization of the two proteins is addressed. In vitro translation of NSP-A and -C RNA produced proteins of about 135 and 23 kDa, respectively. Proteins of similar molecular mass were also detected in immunoprecipitation and western blot analyses of neural and endocrine cells using specific anti-NSP-A or -C antisera; some heterogeneity of NSP-A was observed. NSP-A, but not NSP-C, appeared to be highly phosphorylated and preferentially on serine residues. In immunocytochemical studies, we demonstrated that NSP-A and -C are associated with the endoplasmic reticulum; NSP-A was found to co-localize with SERCA2b, a membrane-associated Ca(2+)-ATPase of the endoplasmic reticulum. In Purkinje cells, we found NSP-immunostaining in the perikaryon, the extensive dendritic tree and the axon, also suggesting association with the smooth endoplasmic reticulum. Biochemical studies of NSP-A provided evidence that NSP-A is strongly associated with microsomal membranes and analysis of deletion mutants of NSP-A revealed that the hydrophobic carboxy-terminal portion of the protein, which is also present in NSP-C, is critical for membrane binding. Through database searches, finally, we found two different NSP-related sequences, one in a sequenced region of human chromosome 19, and the second in a human, pancreatic islet-derived partial cDNA, suggesting that the NSP gene is the prototype of a larger gene family. The results of our studies seem to indicate that the NSP-encoded proteins are novel, membrane-anchored components of the endoplasmic reticulum for which we propose the name reticulons.

scholarly journals Targeting of Rough Endoplasmic Reticulum Membrane Proteins and Ribosomes in Invertebrate Neurons

2002 ◽  
Vol 13 (5) ◽  
pp. 1778-1791 ◽  
Author(s):  
Melissa M. Rolls ◽  
David H. Hall ◽  
Martin Victor ◽  
Ernst H. K. Stelzer ◽  
Tom A. Rapoport
Keyword(s):  
Endoplasmic Reticulum ◽  
Caenorhabditis Elegans ◽  
Membrane Proteins ◽  
Cell Body ◽  
Rough Endoplasmic Reticulum ◽  
Protein Targeting ◽  
Fluorescent Protein ◽  
Cell Types ◽  
Endoplasmic Reticulum Membrane ◽  
Unknown Mechanism

The endoplasmic reticulum (ER) is divided into rough and smooth domains (RER and SER). The two domains share most proteins, but RER is enriched in some membrane proteins by an unknown mechanism. We studied RER protein targeting by expressing fluorescent protein fusions to ER membrane proteins in Caenorhabditis elegans. In several cell types RER and general ER proteins colocalized, but in neurons RER proteins were concentrated in the cell body, whereas general ER proteins were also found in neurites. Surprisingly RER membrane proteins diffused rapidly within the cell body, indicating they are not localized by immobilization. Ribosomes were also concentrated in the cell body, suggesting they may be in part responsible for targeting RER membrane proteins.

A role for smooth endoplasmic reticulum membrane cholesterol ester in determining the intracellular location and regulation of sterol-regulatory-element-binding protein-2

2001 ◽  
Vol 358 (2) ◽  
pp. 415-422 ◽  
Author(s):  
Christopher R. IDDON ◽  
Jane WILKINSON ◽  
Andrew J. BENNETT ◽  
Julie BENNETT ◽  
Andrew M. SALTER ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cholesterol Ester ◽  
Smooth Endoplasmic Reticulum ◽  
Regulatory Element ◽  
Membrane Cholesterol ◽  
Endoplasmic Reticulum Membrane ◽  
Cellular Cholesterol ◽  
Element Binding Protein ◽  
Sterol Regulatory Element ◽  
Coa Reductase

Cellular cholesterol homoeostasis is regulated through proteolysis of the membrane-bound precursor sterol-regulatory-element-binding protein (SREBP) that releases the mature transcription factor form, which regulates gene expression. Our aim was to identify the nature and intracellular site of the putative sterol-regulatory pool which regulates SREBP proteolysis in hamster liver. Cholesterol metabolism was modulated by feeding hamsters control chow, or a cholesterol-enriched diet, or by treatment with simvastatin or with the oral acyl-CoA:cholesterol acyltransferase inhibitor C1-1011 plus cholesterol. The effects of the different treatments on SREBP activation were confirmed by determination of the mRNAs for the low-density lipoprotein receptor and hydroxymethylglutaryl-CoA (HMG-CoA) reductase and by measurement of HMG-CoA reductase activity. The endoplasmic reticulum was isolated from livers and separated into subfractions by centrifugation in self-generating iodixanol gradients. Immunodetectable SREBP-2 accumulated in the smooth endoplasmic reticulum of cholesterol-fed animals. Cholesterol ester levels of the smooth endoplasmic reticulum membrane (but not the cholesterol levels) increased after cholesterol feeding and fell after treatment with simvastatin or C1-1011. The results suggest that an increased cellular cholesterol load causes accumulation of SREBP-2 in the smooth endoplasmic reticulum and, therefore, that membrane cholesterol ester may be one signal allowing exit of the SREBP-2/SREBP-cleavage-regulating protein complex to the Golgi.

scholarly journals The Expanding Role of Mitochondria, Autophagy and Lipophagy in Steroidogenesis

Cells ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 1851
Author(s):  
Geetika Bassi ◽  
Simarjit Kaur Sidhu ◽  
Suresh Mishra
Keyword(s):  
Potential Role ◽  
Cell Types ◽  
Cholesterol Homeostasis ◽  
Cholesterol Transport ◽  
Inner Mitochondrial Membrane ◽  
Mitochondrial Structure ◽  
Steroidogenic Cell ◽  
Start Domain ◽  
Steroidogenic Cells

The fundamental framework of steroidogenesis is similar across steroidogenic cells, especially in initial mitochondrial steps. For instance, the START domain containing protein-mediated cholesterol transport to the mitochondria, and its conversion to pregnenolone by the enzyme P450scc, is conserved across steroidogenic cells. The enzyme P450scc localizes to the inner mitochondrial membrane, which makes the mitochondria essential for steroidogenesis. Despite this commonality, mitochondrial structure, number, and dynamics vary substantially between different steroidogenic cell types, indicating implications beyond pregnenolone biosynthesis. This review aims to focus on the growing roles of mitochondria, autophagy and lipophagy in cholesterol uptake, trafficking and homeostasis in steroidogenic cells and consequently in steroidogenesis. We will focus on these aspects in the context of the physiological need for different steroid hormones and cell-intrinsic inherent features in different steroidogenic cell types beyond mitochondria as a mere site for the beginning of steroidogenesis. The overall goal is to provide an authentic and comprehensive review on the expanding role of steroidogenic cell-intrinsic processes in cholesterol homeostasis and steroidogenesis, and to bring attention to the scientific community working in this field on these promising advancements. Moreover, we will discuss a novel mitochondrial player, prohibitin, and its potential role in steroidogenic mitochondria and cells, and consequently, in steroidogenesis.

scholarly journals Cytoskeleton-Associated Protein 4: Functions Beyond the Endoplasmic Reticulum in Physiology and Disease

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Kevin M. Tuffy ◽  
Sonia Lobo Planey
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Types ◽  
Lipid Homeostasis ◽  
Drug Induced ◽  
Microtubule Network ◽  
Major Function ◽  
Lung Lipid ◽  
Intermediate Compartment ◽  
Rough Er ◽  
Cellular Compartments

Cytoskeleton-associated protein 4 (CKAP4; also known as p63, CLIMP-63, or ERGIC-63) is a 63 kDa, reversibly palmitoylated and phosphorylated, type II transmembrane (TM) protein, originally identified as a resident of the endoplasmic reticulum (ER)/Golgi intermediate compartment (ERGIC). When localized to the ER, a major function of CKAP4 is to anchor rough ER to microtubules, organizing the overall structure of ER with respect to the microtubule network. There is also steadily accumulating evidence for diverse roles for CKAP4 localized outside the ER, including data demonstrating functionality of cell surface forms of CKAP4 in various cell types and of CKAP4 in the nucleus. We will review the recent studies that provide evidence for the existence of CKAP4 in multiple cellular compartments (i.e., ER, plasma membrane, and the nucleus) and discuss CKAP4’s role in the regulation of various physiological and pathological processes, such as interstitial cystitis, drug-induced cytotoxicity, pericullar proteolytic activity, and lung lipid homeostasis.

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