A single conserved proline residue determines the membrane topology of stomatin

2009 ◽  
Vol 418 (3) ◽  
pp. 587-594 ◽  
Author(s):  
Ivan Kadurin ◽  
Stephan Huber ◽  
Stefan Gründer
Keyword(s):  
Ion Channels ◽  
Transmembrane Protein ◽  
Cell Types ◽  
Membrane Topology ◽  
Hairpin Loop ◽  
Hydrophobic Domain ◽  
Proline Residue ◽  
Single Pass ◽  
Loop Topology ◽  
Related Proteins

Stomatin is an integral membrane protein which is widely expressed in many cell types. It is accepted that stomatin has a unique hairpin-loop topology: it is anchored to the membrane with an N-terminal hydrophobic domain and the N- and C-termini are cytoplasmically localized. Stomatin is a prototype for a family of related proteins, containing among others MEC-2 (mechanosensory protein 2) from Caenorhabditis elegans, SLP (stomatin-like protein)-3 and podocin, all of which interact with ion channels to regulate their activity. Members of the stomatin family partly localize in DRMs (detergent-resistant membrane domains) enriched in cholesterol and sphingolipids. It has been proposed that a highly conserved proline residue in the middle of the hydrophobic domain directly binds cholesterol and that cholesterol binding is necessary for the regulation of ion channels. In the present study we show that a small part of the stomatin pool exists as a single-pass transmembrane protein rather than a hairpin-loop protein. The highly conserved proline residue is crucial for adopting the hairpin-loop topology: substitution of this proline residue by serine transfers the whole stomatin pool to the single-pass transmembrane form, which no longer localizes to DRMs. These results suggest that formation of the hairpin loop is inefficient and that the conserved proline residue is indispensable for formation of the hairpin loop. The single-pass transmembrane form exists also for SLP-3 and it should be considered that it mediates part of the physiological functions of stomatin and related proteins.

Control of secretion in anterior pituitary cells--linking ion channels, messengers and exocytosis

1988 ◽  
Vol 139 (1) ◽  
pp. 287-316
Author(s):  
W. T. Mason ◽  
S. R. Rawlings ◽  
P. Cobbett ◽  
S. K. Sikdar ◽  
R. Zorec ◽  
...  
Keyword(s):  
Ion Channels ◽  
Intracellular Calcium ◽  
Anterior Pituitary ◽  
Hormone Secretion ◽  
Cell Types ◽  
Pituitary Cell ◽  
Pituitary Cells ◽  
Calcium Activity ◽  
Anterior Pituitary Cells ◽  
Voltage Dependent

Normal anterior pituitary cells, in their diversity and heterogeneity, provide a rich source of models for secretory function. However, until recently they have largely been neglected in favour of neoplastic, clonal tumour cell lines of pituitary origin, which have enabled a number of studies on supposedly homogeneous cell types. Because many of these lines appear to lack key peptide and neurotransmitter receptors, as well as being degranulated with accompanying abnormal levels of secretion, we have developed a range of normal primary anterior pituitary cell cultures using dispersion and enrichment techniques. By studying lactotrophs, somatotrophs and gonadotrophs we have revealed a number of possible transduction mechanisms by which receptors for hypothalamic peptides and neurotransmitters may control secretion. In particular, the transduction events controlling secretion from pituitary cells may differ fundamentally from those found in other cell types. Patch-clamp recordings in these various pituitary cell preparations have revealed substantial populations of voltage-dependent Na+, Ca2+ and K+ channels which may support action potentials in these cells. Although activation of these channels may gate Ca2+ entry to the cells under some conditions, our evidence taken with that of other laboratories suggests that peptide-receptor interactions leading to hormone secretion occur independently of significant membrane depolarization. Rather, secretion of hormone and rises in intracellular calcium measured with new probes for intracellular calcium activity, can occur in response to hypothalamic peptide activation in the absence of substantial changes in membrane potential. These changes in intracellular calcium activity almost certainly depend on both intracellular and extracellular calcium sources. In addition, strong evidence of a role for multiple intracellular receptors and modulators in the secretory event suggests we should consider the plasma membrane channels important for regulation of hormone secretion to be predominantly agonist-activated, rather than of the more conventional voltage-dependent type. Likewise, evidence from new methods for recording single ion channels suggests the existence of intracellular sites for channel modulation, implying they too may play an important role in secretory regulation. We shall consider new data and new technology which we hope will provide key answers to the many intriguing questions surrounding the control of pituitary hormone secretion. We shall highlight our work with recordings of single ion channels activated by peptides, and recent experiments using imaging of intracellular ionized free calcium.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Calnexin revealed as an ether-a-go-go chaperone by getting mutant worms up and going

2018 ◽  
Vol 150 (8) ◽  
pp. 1059-1061
Author(s):  
Jonathan T. Pierce
Keyword(s):  
Ion Channels ◽  
Dynamic Control ◽  
Cell Types ◽  
K Channel ◽  
Membrane Domains ◽  
Excitable Cells ◽  
Patch Clamp Recording ◽  
Cell Excitability ◽  
Distinct Membrane

The role of ion channels in cell excitability was first revealed in a series of voltage clamp experiments by Hodgkin and Huxley in the 1950s. However, it was not until the 1970s that patch-clamp recording ushered in a revolution that allowed physiologists to witness how ion channels flicker open and closed at angstrom scale and with microsecond resolution. The unexpectedly tight seal made by the patch pipette in the whole-cell configuration later allowed molecular biologists to suck up the insides of identified cells to unveil their unique molecular contents. By refining these techniques, researchers have scrutinized the surface and contents of excitable cells in detail over the past few decades. However, these powerful approaches do not discern which molecules are responsible for the dynamic control of the genesis, abundance, and subcellular localization of ion channels. In this dark territory, teams of unknown and poorly understood molecules guide specific ion channels through translation, folding, and modification, and then they shuttle them toward and away from distinct membrane domains via different subcellular routes. A central challenge in understanding these processes is the likelihood that these diverse regulatory molecules may be specific to ion channel subtypes, cell types, and circumstance. In work described in this issue, Bai et al. (2018. J. Gen. Physiol. https://doi.org/10.1085/jgp.201812025) begin to shed light on the biogenesis of UNC-103, a K+ channel found in Caenorhabditis elegans.

scholarly journals Synthesis of p36 and p35 is increased when U-937 cells differentiate in culture but expression is not inducible by glucocorticoids.

1989 ◽  
Vol 9 (1) ◽  
pp. 232-240 ◽  
Author(s):  
C M Isacke ◽  
R A Lindberg ◽  
T Hunter
Keyword(s):  
Tyrosine Kinases ◽  
Myeloid Cell ◽  
Cell Types ◽  
Culture Conditions ◽  
Actin Binding ◽  
Myeloid Cell Line ◽  
Related Proteins ◽  
Cortical Cytoskeleton ◽  
Inflammatory Action ◽  
Human Specific

p36 and p35 are distinct but related proteins that share many structural and biochemical features which were first identified as major substrates for protein-tyrosine kinases. Subsequently, both proteins have been shown to be Ca2+-, phospholipid-, and F-actin-binding proteins that underlie the plasma membrane and are associated with the cortical cytoskeleton. Recent reports have claimed that these proteins function as lipocortins, i.e., phospholipase A2 inhibitors that mediate the anti-inflammatory action of glucocorticoids. To investigate this possibility and to learn more about the functions of p36 and p35, we used human-specific anti-p36 and anti-p35 monoclonal antibodies to determine whether the expression or secretion of either protein was inducible by dexamethasone in the human U-937 myeloid cell line and in other human cell types. Additionally, we examined the levels of mRNA for both proteins. No effect of dexamethasone was observed on p36 or p35 expression at either the mRNA or protein level, nor were these proteins secreted under any of the culture conditions investigated. However, it was observed that in these cells the rate of synthesis and accumulation of both proteins was increased when the U-937 cells were induced to differentiate in culture to adherent macrophagelike cells. This offers a model system with which to study the control of p36 and p35 expression.

scholarly journals Ion Channels and Early Development of Neural Cells

1998 ◽  
Vol 78 (2) ◽  
pp. 307-337 ◽  
Author(s):  
KUNITARO TAKAHASHI ◽  
YASUSHI OKAMURA
Keyword(s):  
Ion Channels ◽  
Early Development ◽  
Cellular Differentiation ◽  
Neural Induction ◽  
Cell Types ◽  
Simple System ◽  
Optical Methods ◽  
Transcriptional Level ◽  
Neural Cells ◽  
Embryonic Cells

Takahashi, Kunitaro, and Yasushi Okamura. Ion Channels and Early Development of Neural Cells. Physiol. Rev. 78: 307–337, 1998. — In this review, we underscore the merits of using voltage-dependent ion channels as markers for neuronal differentiation from the early stages of uncommitted embryonic blastomeres. Furthermore, a fairly large part of the review is devoted to the descriptions of the establishment of a simple model system for neural induction derived from the cleavage-arrested eight-cell ascidian embryo by pairing a single ectodermal with a single vegetal blastomere as a competent and an inducer cell, respectively. The descriptions are focused particularly on the early developmental processes of various ion channels in neuronal and other excitable membranes observed in this extraordinarily simple system, and we compare these results with those in other significant and definable systems for neural differentiation. It is stressed that this simple system, for which most of the electronic and optical methods and various injection experiments are applicable, may be useful for future molecular physiological studies on the intracellular process of differentiation of the early embryonic cells. We have also highlighted the importance of suppressive mechanisms for cellular differentiation from the experimental results, such as epidermal commitment of the cleavage-arrested one-cell Halocynthia embryos or suppression of epidermal-specific transcription of inward rectifier channels by neural induction signals. It was suggested that reciprocal suppressive mechanisms at the transcriptional level may be one of the key processes for cellular differentiation, by which exclusivity of cell types is maintained.

scholarly journals Site-specific deacylation by ABHD17a controls BK channel splice variant activity

2020 ◽  
Vol 295 (49) ◽  
pp. 16487-16496 ◽  
Author(s):  
Heather McClafferty ◽  
Hamish Runciman ◽  
Michael J. Shipston
Keyword(s):  
Ion Channels ◽  
Ion Channel ◽  
Membrane Trafficking ◽  
Transmembrane Protein ◽  
Surface Expression ◽  
Bk Channels ◽  
Bk Channel ◽  
Site Specific ◽  
And Function ◽  
A Site

S-Acylation, the reversible post-translational lipid modification of proteins, is an important mechanism to control the properties and function of ion channels and other polytopic transmembrane proteins. However, although increasing evidence reveals the role of diverse acyl protein transferases (zDHHC) in controlling ion channel S-acylation, the acyl protein thioesterases that control ion channel deacylation are very poorly defined. Here we show that ABHD17a (α/β-hydrolase domain-containing protein 17a) deacylates the stress-regulated exon domain of large conductance voltage- and calcium-activated potassium (BK) channels inhibiting channel activity independently of effects on channel surface expression. Importantly, ABHD17a deacylates BK channels in a site-specific manner because it has no effect on the S-acylated S0–S1 domain conserved in all BK channels that controls membrane trafficking and is deacylated by the acyl protein thioesterase Lypla1. Thus, distinct S-acylated domains in the same polytopic transmembrane protein can be regulated by different acyl protein thioesterases revealing mechanisms for generating both specificity and diversity for these important enzymes to control the properties and functions of ion channels.

scholarly journals Dorsal, a Drosophila Rel-like protein, is phosphorylated upon activation of the transmembrane protein Toll.

1994 ◽  
Vol 14 (6) ◽  
pp. 3559-3568 ◽  
Author(s):  
S K Gillespie ◽  
S A Wasserman
Keyword(s):  
Nuclear Import ◽  
Intracellular Signaling ◽  
Kinase Activity ◽  
Transmembrane Protein ◽  
Immunoblot Analysis ◽  
Phosphorylation State ◽  
Intracellular Signaling Pathway ◽  
Time Period ◽  
Intracellular Proteins ◽  
Related Proteins

The nuclear import of dorsal, a Drosophila Rel homolog, is directed by a spatially restricted extracellular ligand in blastoderm embryos. We have demonstrated both that dorsal is an embryonic phosphoprotein and that its phosphorylation state is regulated by an intracellular signaling pathway initiated by the transmembrane receptor Toll. Immunoblot analysis of cytoplasm from precisely staged embryos revealed that the phosphorylation state of dorsal is altered during the time period that Toll is activated. Moreover, mutations that constitutively activate Toll stimulated dorsal phosphorylation, while mutations that block Toll activation reduced the level of dorsal phosphorylation. We further demonstrated that signal-dependent dorsal phosphorylation is modulated by three intracellular proteins, pelle, tube, and cactus. Using double-mutant embryos, we then explored the nature of the kinase activity responsible for dorsal phosphorylation. We found that free dorsal is a substrate for a signal-independent kinase activity. In addition, our results imply that dorsal is a substrate for a Toll-dependent kinase. These results are consistent with the hypothesis that phosphorylation of Rel-related proteins may be required for the proper nuclear localization and transcriptional activity of these proteins.

scholarly journals The TP53INP2 Protein Is Required for Autophagy in Mammalian Cells

2009 ◽  
Vol 20 (3) ◽  
pp. 870-881 ◽  
Author(s):  
Jonathan Nowak ◽  
Cendrine Archange ◽  
Joël Tardivel-Lacombe ◽  
Pierre Pontarotti ◽  
Marie-Josèphe Pébusque ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Homo Sapiens ◽  
Transmembrane Protein ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Gene Encoding ◽  
Related Proteins ◽  
Interfering Rna ◽  
Bioinformatic Approach ◽  
Hybrid Screening

Using a bioinformatic approach, we identified a TP53INP1-related gene encoding a protein with 30% identity with tumor protein 53-induced nuclear protein 1 (TP53INP1), which was named TP53INP2. TP53INP1 and TP53INP2 sequences were found in several species ranging from Homo sapiens to Drosophila melanogaster, but orthologues were found neither in earlier eukaryotes nor in prokaryotes. To gain insight into the function of the TP53INP2 protein, we carried out a yeast two-hybrid screening that showed that TP53INP2 binds to the LC3-related proteins GABARAP and GABARAP-like2, and then we demonstrated by coimmunoprecipitation that TP53INP2 interacts with these proteins, as well as with LC3 and with the autophagosome transmembrane protein VMP1. TP53INP2 translocates from the nucleus to the autophagosome structures after activation of autophagy by rapamycin or starvation. Also, we showed that TP53INP2 expression is necessary for autophagosome development because its small interfering RNA-mediated knockdown strongly decreases sensitivity of mammalian cells to autophagy. Finally, we found that interactions between TP53INP2 and LC3 or the LC3-related proteins GABARAP and GABARAP-like2 require autophagy and are modulated by wortmannin as judged by bioluminescence resonance energy transfer assays. We suggest that TP53INP2 is a scaffold protein that recruits LC3 and/or LC3-related proteins to the autophagosome membrane by interacting with the transmembrane protein VMP1. It is concluded that TP53INP2 is a novel gene involved in the autophagy of mammalian cells.

Ion Channels and Cell Volume Regulation: Chaos in an Organized System

Physiology ◽  
1990 ◽  
Vol 5 (3) ◽  
pp. 112-119 ◽  
Author(s):  
SA Lewis ◽  
P Donaldson
Keyword(s):  
Ion Channels ◽  
Cell Volume ◽  
Volume Regulation ◽  
Cell Volume Regulation ◽  
Cell Types ◽  
Initial Increase ◽  
Normal Value ◽  
Basic Strategy

Exposure of many vertebrate cells to solutions more dilute or concentrated than the physiological "norm" results in an initial increase or decrease in cell volume followed by a recovery of volume toward a normal value. Although the basic strategy for volume regulation is the same for cell types studied, the mechanism by which the cell regulates ion channels appears to be tissue dependent.

scholarly journals IGFBP-3/IGFBP-3 Receptor System as an Anti-Tumor and Anti-Metastatic Signaling in Cancer

Cells ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 1261 ◽  
Author(s):  
Qing Cai ◽  
Mikhail Dozmorov ◽  
Youngman Oh
Keyword(s):  
Therapeutic Potential ◽  
Transmembrane Protein ◽  
Biological Significance ◽  
Cell Types ◽  
Receptor System ◽  
Post Translational Modifications ◽  
Major Carrier ◽  
Assay Methods ◽  
Underlying Mechanisms ◽  
Igfbp 3

Insulin-like growth factor binding protein-3 (IGFBP-3) is a p53 tumor suppressor-regulated protein and a major carrier for IGFs in circulation. Among six high-affinity IGFBPs, which are IGFBP-1 through 6, IGFBP-3 is the most extensively investigated IGFBP species with respect to its IGF/IGF-I receptor (IGF-IR)-independent biological actions beyond its endocrine/paracrine/autocrine role in modulating IGF action in cancer. Disruption of IGFBP-3 at transcriptional and post-translational levels has been implicated in the pathophysiology of many different types of cancer including breast, prostate, and lung cancer. Over the past two decades, a wealth of evidence has revealed both tumor suppressing and tumor promoting effects of IGF/IGF-IR-independent actions of IGFBP-3 depending upon cell types, post-translational modifications, and assay methods. However, IGFBP-3′s anti-tumor function has been well accepted due to identification of functional IGFBP-3-interacting proteins, putative receptors, or crosstalk with other signaling cascades. This review mainly focuses on transmembrane protein 219 (TMEM219), which represents a novel IGFBP-3 receptor mediating antitumor effect of IGFBP-3. Furthermore, this review delineates the potential underlying mechanisms involved and the subsequent biological significance, emphasizing the clinical significance of the IGFBP-3/TMEM219 axis in assessing both the diagnosis and the prognosis of cancer as well as the therapeutic potential of TMEM219 agonists for cancer treatment.

scholarly journals Cells Derived from Human Long Bone Appear More Differentiated and More Actively Stimulate Osteoclastogenesis Compared to Alveolar Bone-Derived Cells

2020 ◽  
Vol 21 (14) ◽  
pp. 5072
Author(s):  
Cindy Kelder ◽  
Cornelis J. Kleverlaan ◽  
Marjolijn Gilijamse ◽  
Astrid D. Bakker ◽  
Teun J. de Vries
Keyword(s):  
Tissue Engineering ◽  
Mononuclear Cells ◽  
Alveolar Bone ◽  
Bone Cells ◽  
Transmembrane Protein ◽  
Cell Types ◽  
Long Bone ◽  
Long Bones ◽  
Peripheral Blood Mononuclear ◽  
Alveolar Bone Cells

Osteoblasts derived from mouse skulls have increased osteoclastogenic potential compared to long bone osteoblasts when stimulated with 1,25(OH)2 vitamin D3 (vitD3). This indicates that bone cells from specific sites can react differently to biochemical signals, e.g., during inflammation or as emitted by bioactive bone tissue-engineering constructs. Given the high turn-over of alveolar bone, we hypothesized that human alveolar bone-derived osteoblasts have an increased osteogenic and osteoclastogenic potential compared to the osteoblasts derived from long bone. The osteogenic and osteoclastogenic capacity of alveolar bone cells and long bone cells were assessed in the presence and absence of osteotropic agent vitD3. Both cell types were studied in osteogenesis experiments, using an osteogenic medium, and in osteoclastogenesis experiments by co-culturing osteoblasts with peripheral blood mononuclear cells (PBMCs). Both osteogenic and osteoclastic markers were measured. At day 0, long bones seem to have a more late-osteoblastic/preosteocyte-like phenotype compared to the alveolar bone cells as shown by slower proliferation, the higher expression of the matrix molecule Osteopontin (OPN) and the osteocyte-enriched cytoskeletal component Actin alpha 1 (ACTA1). This phenotype was maintained during the osteogenesis assays, where long bone-derived cells still expressed more OPN and ACTA1. Under co-culture conditions with PBMCs, long bone cells also had a higher Tumor necrose factor-alfa (TNF-α) expression and induced the formation of osteoclasts more than alveolar bone cells. Correspondingly, the expression of osteoclast genes dendritic cell specific transmembrane protein (DC-STAMP) and Receptor activator of nuclear factor kappa-Β ligand (RankL) was higher in long bone co-cultures. Together, our results indicate that long bone-derived osteoblasts are more active in bone-remodeling processes, especially in osteoclastogenesis, than alveolar bone-derived cells. This indicates that tissue-engineering solutions need to be specifically designed for the site of application, such as defects in long bones vs. the regeneration of alveolar bone after severe periodontitis.

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