scholarly journals The outer segment serves as a default destination for the trafficking of membrane proteins in photoreceptors

2008 ◽  
Vol 183 (3) ◽  
pp. 485-498 ◽  
Author(s):  
Sheila A. Baker ◽  
Mohammad Haeri ◽  
Peter Yoo ◽  
Sidney M. Gospe ◽  
Nikolai P. Skiba ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Proteins ◽  
Outer Segment ◽  
The Other ◽  
Visual Signals ◽  
Its Sequence ◽  
Specific Targeting ◽  
New Material ◽  
Targeting Signals ◽  
Syntaxin 3

Photoreceptors are compartmentalized neurons in which all proteins responsible for evoking visual signals are confined to the outer segment. Yet, the mechanisms responsible for establishing and maintaining photoreceptor compartmentalization are poorly understood. Here we investigated the targeting of two related membrane proteins, R9AP and syntaxin 3, one residing within and the other excluded from the outer segment. Surprisingly, we have found that only syntaxin 3 has targeting information encoded in its sequence and its removal redirects this protein to the outer segment. Furthermore, proteins residing in the endoplasmic reticulum and mitochondria were similarly redirected to the outer segment after removing their targeting signals. This reveals a pattern where membrane proteins lacking specific targeting information are delivered to the outer segment, which is likely to reflect the enormous appetite of this organelle for new material necessitated by its constant renewal. This also implies that every protein residing outside the outer segment must have a means to avoid this “default” trafficking flow.

scholarly journals Cycles of autoubiquitination and deubiquitination regulate the ERAD ubiquitin ligase Hrd1

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Brian G Peterson ◽  
Morgan L Glaser ◽  
Tom A Rapoport ◽  
Ryan D Baldridge
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Proteins ◽  
Ubiquitin Ligase ◽  
Ground State ◽  
Inhibitory Effect ◽  
The Other ◽  
Misfolded Proteins ◽  
Deubiquitinating Enzyme ◽  
Transmembrane Segment

Misfolded proteins in the lumen of the endoplasmic reticulum (ER) are retrotranslocated into the cytosol and polyubiquitinated before being degraded by the proteasome. The multi-spanning ubiquitin ligase Hrd1 forms the retrotranslocation channel and associates with three other membrane proteins (Hrd3, Usa1, Der1) of poorly defined function. The Hrd1 channel is gated by autoubiquitination, but how Hrd1 escapes degradation by the proteasome and returns to its inactive ground state is unknown. Here, we show that autoubiquitination of Hrd1 is counteracted by Ubp1, a deubiquitinating enzyme that requires its N-terminal transmembrane segment for activity towards Hrd1. The Hrd1 partner Hrd3 serves as a brake for autoubiquitination, while Usa1 attenuates Ubp1’s deubiquitination activity through an inhibitory effect of its UBL domain. These results lead to a model in which the Hrd1 channel is regulated by cycles of autoubiquitination and deubiquitination, reactions that are modulated by the other components of the Hrd1 complex.

Taraxacum sect. Orientalia (Compositae-Crepidinae) and the West Himalayan dandelions: A new interpretation

Phytotaxa ◽  
2017 ◽  
Vol 312 (1) ◽  
pp. 1 ◽  
Author(s):  
JAN KIRSCHNER ◽  
JAN ŠTĚPÁNEK ◽  
VOJTĚCH ZEISEK
Keyword(s):  
Sequence Analysis ◽  
The Other ◽  
Its Sequence ◽  
Nrdna Its ◽  
The West ◽  
West Himalaya ◽  
Its Sequence Analysis ◽  
New Material ◽  
New Interpretation ◽  
Herbarium Collections

The Taraxacum flora of the West Himalaya represents one of the dandelion diversity hotspots, with at least 17 sections and about 150 known species. A number of names published from that region were referred to T. sect. Orientalia Handel-Mazzetti in the literature. All these names are revised and newly interpreted, with emphasis on plants erroneously determined as T. stenolepium. The revision is based on both older herbarium collections and a new material from expeditions of the late L. Klimeš. A new section, T. sect. Squamulosa, is recognized. An nrDNA ITS sequence analysis including the only sexual member of T. section Squamulosa and the other sexual taxa known in Taraxacum shows a separate position of T. sect. Squamulosa. The new section is compared with sections Primigenia, Coronata and Orientalia. Amended descriptions, range extensions and new interpretations are presented for another seven species previously mistakenly referred to T. sect. Orientalia. The true T. sect. Orientalia is analysed and briefly characterized; it is shown to be absent from the West Himalaya.

scholarly journals Syntaxin 3 is essential for photoreceptor outer segment protein trafficking and survival

2020 ◽  
Vol 117 (34) ◽  
pp. 20615-20624
Author(s):  
Mashal Kakakhel ◽  
Lars Tebbe ◽  
Mustafa S. Makia ◽  
Shannon M. Conley ◽  
David M. Sherry ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Protein Trafficking ◽  
Outer Segment ◽  
Functional Decline ◽  
Structural Defects ◽  
Photoreceptor Outer Segment ◽  
Photoreceptor Membrane ◽  
Synaptic Region ◽  
Syntaxin 3

Trafficking of photoreceptor membrane proteins from their site of synthesis in the inner segment (IS) to the outer segment (OS) is critical for photoreceptor function and vision. Here we evaluate the role of syntaxin 3 (STX3), in trafficking of OS membrane proteins such as peripherin 2 (PRPH2) and rhodopsin. Photoreceptor-specificStx3knockouts [Stx3f/f(iCre75)andStx3f/f(CRX-Cre)] exhibited rapid, early-onset photoreceptor degeneration and functional decline characterized by structural defects in IS, OS, and synaptic terminals. Critically, in the absence of STX3, OS proteins such as PRPH2, the PRPH2 binding partner, rod outer segment membrane protein 1 (ROM1), and rhodopsin were mislocalized along the microtubules to the IS, cell body, and synaptic region. We find that the PRPH2 C-terminal domain interacts with STX3 as well as other photoreceptor SNAREs, and our findings indicate that STX3 is an essential part of the trafficking pathway for both disc (rhodopsin) and rim (PRPH2/ROM1) components of the OS.

Compound Symbiosis in Peridinium Balticum

1973 ◽  
Vol 31 ◽  
pp. 500-501
Author(s):  
R. N. Tomas
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
The Other ◽  
Exact Nature ◽  
Symbiotic Relationship

Peridinium balticum appears to be unusual among the dinoflagellates in that it possesses two DNA-containing structures as determined by histochemical techniques. Ultrastructurally, the two dissimilar nuclei are contained within different protoplasts; one of the nuclei is characteristically dinophycean in nature, while the other is characteristically eucaryotic. The chloroplasts observed within P. balticum are intrinsic to an eucaryotic photosynthetic endosymbiont and not to the dinoflagellate. These organelles are surrounded by outpocketings of endoplasmic reticulum which are continuous with the eucaryotic nuclear envelope and are characterized by thylakoids composed of three apposed lamellae. Girdle lamellae and membranebounded interlamellar pyrenoids are also present. Only the plasmalemma of the endosymbiont segregates its protoplast from that of the dinophycean cytoplasm. The exact nature of this symbiotic relationship is at present not known.

Golgi Apparatus and Melanogenesis: Ultrastructural Study of a Human Cellular Blue Nevus (Melanocytoma)

1973 ◽  
Vol 31 ◽  
pp. 380-381
Author(s):  
S.R. Allegra
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Ultrastructural Study ◽  
The Other ◽  
Blue Nevus ◽  
Normal Complement ◽  
Golgi Vesicles ◽  
Golgi System ◽  
The Subject ◽  
Cellular Blue Nevus

The respective roles of the ribo somes, endoplasmic reticulum, Golgi apparatus and perhaps nucleus in the synthesis and maturation of melanosomes is still the subject of some controversy. While the early melanosomes (premelanosomes) have been frequently demonstrated to originate as Golgi vesicles, it is undeniable that these structures can be formed in cells in which Golgi system is not found. This report was prompted by the findings in an essentially amelanotic human cellular blue nevus (melanocytoma) of two distinct lines of melanocytes one of which was devoid of any trace of Golgi apparatus while the other had normal complement of this organelle.

TMCC3 localizes at the three-way junctions for the proper tubular network of the endoplasmic reticulum

2019 ◽  
Vol 476 (21) ◽  
pp. 3241-3260
Author(s):  
Sindhu Wisesa ◽  
Yasunori Yamamoto ◽  
Toshiaki Sakisaka
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Proteins ◽  
Membrane Protein ◽  
Mammalian Cells ◽  
Coiled Coil ◽  
Transmembrane Domains ◽  
Domain Family ◽  
Coiled Coil Domain ◽  
U2os Cells ◽  
Er Membrane

The tubular network of the endoplasmic reticulum (ER) is formed by connecting ER tubules through three-way junctions. Two classes of the conserved ER membrane proteins, atlastins and lunapark, have been shown to reside at the three-way junctions so far and be involved in the generation and stabilization of the three-way junctions. In this study, we report TMCC3 (transmembrane and coiled-coil domain family 3), a member of the TEX28 family, as another ER membrane protein that resides at the three-way junctions in mammalian cells. When the TEX28 family members were transfected into U2OS cells, TMCC3 specifically localized at the three-way junctions in the peripheral ER. TMCC3 bound to atlastins through the C-terminal transmembrane domains. A TMCC3 mutant lacking the N-terminal coiled-coil domain abolished localization to the three-way junctions, suggesting that TMCC3 localized independently of binding to atlastins. TMCC3 knockdown caused a decrease in the number of three-way junctions and expansion of ER sheets, leading to a reduction of the tubular ER network in U2OS cells. The TMCC3 knockdown phenotype was partially rescued by the overexpression of atlastin-2, suggesting that TMCC3 knockdown would decrease the activity of atlastins. These results indicate that TMCC3 localizes at the three-way junctions for the proper tubular ER network.

scholarly journals Activation of the lac Repressor in the Transgenic Mouse

Genetics ◽  
1997 ◽  
Vol 147 (1) ◽  
pp. 297-304
Author(s):  
Heidi Scrable ◽  
Peter J Stambrook
Keyword(s):  
Copy Number ◽  
Methylation Status ◽  
Lac Repressor ◽  
The Other ◽  
Lac Operon ◽  
Normal Process ◽  
Divergent Sequence ◽  
Somatic Tissues ◽  
New Material ◽  
Bacterial Sequence

Abstract We have introduced sequences encoding the lac repressor of Escherichia coli into the genome of the mouse. One sequence was derived from the bacterial lac operon and the other was created by reencoding the amino acid sequence of lacI with mammalian codons. Both versions are driven by an identical promoter fragment derived from the human β-actin locus and were microinjected into genetically identical pronuclear stage embryos. All transgenes utilizing the bacterial coding sequence were transcriptionally silent in all somatic tissues tested. The sequence re-encoded with mammalian codons was transcriptionally active at all transgene loci and expressed ubiquitously. Using methylation-sensitive enzymes, we have determined the methylation status of lac repressor transgenes encoded by either the bacterial or mammalian sequence. The highly divergent bacterial sequence was hypermethylated at all transgene loci, while the mammalian sequence was only hypermethylated at a high copy number locus. This may reflect a normal process that protects the genome from acquiring new material that has an abnormally divergent sequence or structure.

scholarly journals Craniofacial Diseases Caused by Defects in Intracellular Trafficking

Genes ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 726
Author(s):  
Chung-Ling Lu ◽  
Jinoh Kim
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Proteins ◽  
Intracellular Trafficking ◽  
Critical Role ◽  
Treatment Strategies ◽  
Soluble Proteins ◽  
Genes Encoding ◽  
Membrane Bound ◽  
Signaling Receptors ◽  
Craniofacial Morphogenesis

Cells use membrane-bound carriers to transport cargo molecules like membrane proteins and soluble proteins, to their destinations. Many signaling receptors and ligands are synthesized in the endoplasmic reticulum and are transported to their destinations through intracellular trafficking pathways. Some of the signaling molecules play a critical role in craniofacial morphogenesis. Not surprisingly, variants in the genes encoding intracellular trafficking machinery can cause craniofacial diseases. Despite the fundamental importance of the trafficking pathways in craniofacial morphogenesis, relatively less emphasis is placed on this topic, thus far. Here, we describe craniofacial diseases caused by lesions in the intracellular trafficking machinery and possible treatment strategies for such diseases.

scholarly journals Septin-dependent compartmentalization of the endoplasmic reticulum during yeast polarized growth

2005 ◽  
Vol 169 (6) ◽  
pp. 897-908 ◽  
Author(s):  
Cosima Luedeke ◽  
Stéphanie Buvelot Frei ◽  
Ivo Sbalzarini ◽  
Heinz Schwarz ◽  
Anne Spang ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Membrane Proteins ◽  
Diffusion Barriers ◽  
Yeast Cells ◽  
Dependent Manner ◽  
Protein Diffusion ◽  
Ultrastructural Studies ◽  
Bud Neck ◽  
Er Membrane

Polarized cells frequently use diffusion barriers to separate plasma membrane domains. It is unknown whether diffusion barriers also compartmentalize intracellular organelles. We used photobleaching techniques to characterize protein diffusion in the yeast endoplasmic reticulum (ER). Although a soluble protein diffused rapidly throughout the ER lumen, diffusion of ER membrane proteins was restricted at the bud neck. Ultrastructural studies and fluorescence microscopy revealed the presence of a ring of smooth ER at the bud neck. This ER domain and the restriction of diffusion for ER membrane proteins through the bud neck depended on septin function. The membrane-associated protein Bud6 localized to the bud neck in a septin-dependent manner and was required to restrict the diffusion of ER membrane proteins. Our results indicate that Bud6 acts downstream of septins to assemble a fence in the ER membrane at the bud neck. Thus, in polarized yeast cells, diffusion barriers compartmentalize the ER and the plasma membrane along parallel lines.

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