In cell biology, a vesicle is a small ..
phosphate complexes in the plasma membrane mediated in part by a protein called annexins
Chp 2 - CELLS Flashcards | Quizlet
The mechanism for transporting newly synthesized proteins is highly conserved from bacteria to mammals. A key difference, however, is that bacteria translocate the proteins directly across the plasma membrane to the outside world, whereas eukaryotic cells translocate them into a specialized intracellular organelle, the endoplasmic reticulum. Newly synthesized proteins are conveyed from the endoplasmic reticulum to the cell surface via a series of carrier vesicles. It is therefore useful to consider prokaryotic and eukaryotic protein secretion separately.
This nucleus consists of highly specialized cell organelles that take care of storing the cell's hereditary material (DNA) and also coordination of different cell activities like protein synthesis, cell division, growth, etc.
Cell Export - Exocytosis - CellBiology
To take correctly folded and oligomerized proteins from the ER, a vesicle forms in the transitional elements and includes proteins to be exported, but excludes resident proteins of the ER lumen, such as BiP (20). The coat that causes the vesicle to form is now known as COPII. Yeast COPII contains four subunits, sec31p, sec13p, sec23p, and sec24p (see sec mutants). Assembly of a COPII coat requires a small GTPase, Sar1, and a guanine nucleotide exchange factor, Sec12p, in the ER membrane (12) (Fig. 4). The coated vesicle leaving the Golgi carries with it a complement of v-SNARE molecules (see Exocytosis) to allow it to fuse with the cis-Golgi network. In yeast, these are Sec22p, Bos1p, and Bet1p. Resident proteins such as BiP may be excluded from the lumen of the coated vesicle because they are oligomerized into complexes that are too big to enter the small vesicle. To some extent, exported proteins are those that lack a retention signal and so are not retained in the ER. Export of secreted proteins would then be by default, because they lack information to go anywhere else. There is evidence, however, that positive sorting occurs (21) (Fig. 5). In yeast, the secreted protein invertase is recognized by a membrane-bound ER protein (Emp24p) that is required for its transport to the Golgi (22). Furthermore, cargo proteins are concentrated as they leave the ER (23, 24). Since most soluble resident proteins in the ER lumen are not glycosylated, an attractive hypothesis is that exported proteins are recognized by a lectin, which concentrates them in budding vesicles. A protein, ERGIC-53, recycles between the ER and the Golgi and is a lectin with the capacity to bind the mannose residues found on newly synthesized secretory proteins (25). Proteins such as ERGIC-53 might bind secreted proteins and actively carry them to the Golgi complex, in the same way that the mannose phosphate receptor carries newly formed lysosomal enzymes to the prelysosomal compartment.
The third type of glycosylation results in the formation of proteoglycans. Proteoglycans are formed by the addition of xylose to serine residues as the protein moves from the ER to the Golgi (27), followed by the addition of a long, highly charged, unbranched oligosaccharide called a glycosaminoglycan. Glycosaminoglycans are polymers of a disaccharide unit, one of which is usually uronic acid. The other member of the oligosaccharide pair varies, depending on the type of glycosaminoglycan. Part of the strong negative charge on the proteoglycans is due to the addition of sulfate groups to the glycosaminoglycans. Sulfate can also be added directly to tyrosine residues on secreted proteins. Sulfation of proteins only takes place in the late Golgi. Radioactive sulfate is thus commonly used to label exported proteins selectively and to identify a set of proteins at a late Golgi step of transport. Glycosaminoglycan chain synthesis can be initiated in the late Golgi by growing cells in the presence of a membrane-permeable derivation of xylose (28). This technique has also been used to identify membrane traffic from the late Golgi to the surface of the cell.
The Dynamic Cell; MCB - Model of protein synthesis on circular ..
Autophagy is a degradative process conserved among all eukaryotic cells and is required for the rapid degradation of large portions of the cytoplasm and unnecessary or damaged organelles in the lysosome lumen. It has long been known that this catabolic pathway is essential to generate an internal pool of nutrients that permit cells to survive during prolonged periods of starvation. Recent studies however, have revealed that autophagy actively participates in other cellular processes such as development, cellular differentiation and rearrangement, aging, elimination of aberrant structures and type II programmed cell death, as well as contributing to the cell’s defense against pathogens (both viruses and bacteria) and tumors. Consequently, defects in this protective barrier correlate with a growing list of diseases, including cancer, neurodegenerative disorders such as Huntington’s, Parkinson’s and Alzheimer’s diseases, and cardiomyopathies.
The main morphological feature of autophagy is the sequestration of the cargo targeted for destruction by a large cytosolic double-membrane vesicle called autophagosome that delivers it into the lysosome/vacuole interior for destruction. Despite the identification of many specific components, the molecular mechanism that directs formation of the sequestering vesicles remains largely unknown.
Adv Exp Med Biol. 2013;986:209-20. doi: 10.1007/978-94-007-4719-7_11.
Cannabinoid signaling in glioma cells.
Ellert-Miklaszewska A1, Ciechomska I, Kaminska B.
Cannabinoids are a group of structurally heterogeneous but pharmacologically related compounds, including plant-derived cannabinoids, synthetic substances and endogenous cannabinoids, such as anandamide and 2-arachidonoylglycerol. Cannabinoids elicit a wide range of central and peripheral effects mostly mediated through cannabinoid receptors. There are two types of specific G(i/o)-protein-coupled receptors cloned so far, called CB1 and CB2, although an existence of additional cannabinoid-binding receptors has been suggested. CB1 and CB2 differ in their predicted amino acid sequence, tissue distribution, physiological role and signaling mechanisms. Significant alterations of a balance in the cannabinoid system between the levels of endogenous ligands and their receptors occur during malignant transformation in various types of cancer, including gliomas. Cannabinoids exert anti-proliferative action in tumor cells. Induction of cell death by cannabinoid treatment relies on the generation of a pro-apoptotic sphingolipid ceramide and disruption of signaling pathways crucial for regulation of cellular proliferation, differentiation or apoptosis. Increased ceramide levels lead also to ER-stress and autophagy in drug-treated glioblastoma cells.
The classical mechanism of cell secretion ..
or main terminal branch of the general secretory pathway, ..
specific active ..
Bacterial effector protein; Bacterial outer membrane vesicles;
Secretion - Wikipedia
16/01/2018 · Cell - Secretory vesicles: ..
exports other classes of RNA involved in the mechanisms of protein synthesis
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