scholarly journals Small disulfide loops in peptide hormones mediate self-aggregation and secretory granule sorting

2021 ◽  
Author(s):  
Jennifer Reck ◽  
Nicole Beuret ◽  
Erhan Demirci ◽  
Cristina Prescianotto-Baschong ◽  
Martin Spiess
Keyword(s):  
Endoplasmic Reticulum ◽  
Secretory Granule ◽  
Secretory Granules ◽  
Peptide Hormones ◽  
Secreted Proteins ◽  
Reporter Protein ◽  
Granule Formation ◽  
Functional Amyloids ◽  
Golgi Network ◽  
Self Aggregation

ABSTRACTUnlike constitutively secreted proteins, peptide hormones are stored in densely packed secretory granules, before regulated release upon stimulation. Secretory granules are formed at the trans-Golgi network (TGN) by self-aggregation of prohormones as functional amyloids. The nonapeptide hormone vasopressin, which forms a small disulfide loop, was shown to be responsible for granule formation of its precursor in the TGN as well as for toxic fibrillar aggregation of unfolded mutants in the endoplasmic reticulum (ER). Several other hormone precursors also contain similar small disulfide loops suggesting their function as a general device to mediate aggregation for granule biogenesis. To test this hypothesis, we studied the capacity of small disulfide loops of different hormone precursors to mediate aggregation in the ER and the TGN. They indeed induced ER aggregation although to different extents in Neuro-2a and COS-1 cells. Fused to a constitutively secreted reporter protein, they also promoted sorting into secretory granules, enhanced stimulated secretion, and increased Lubrol insolubility in AtT20 cells. These results support the hypothesis that small disulfide loops act as novel signals for secretory granule biogenesis and sorting by self-aggregation.

scholarly journals Microtubules and protein secretion in rat lacrimal glands: localization of short-term effects of colchicine on the secretory process.

1982 ◽  
Vol 95 (1) ◽  
pp. 105-117 ◽  
Author(s):  
S Busson-Mabillot ◽  
A M Chambaut-Guérin ◽  
L Ovtracht ◽  
P Muller ◽  
B Rossignol
Keyword(s):  
Endoplasmic Reticulum ◽  
Secretory Granule ◽  
Protein Secretion ◽  
Rough Endoplasmic Reticulum ◽  
Protein Transport ◽  
Secretory Granules ◽  
Secretory Protein ◽  
Protein Release ◽  
Secretory Process ◽  
Granule Formation

The pathway and kinetics of the secretory protein transport in rat lacrimal exorbital gland have been established by an in vitro time-course radioautographic study of pulse-labeled protein secretion. The colchicine-sensitive steps have been localized by using the drug at various times with respect to the pulse labeling of proteins. Colchicine (10 microM) does not block any step of the secretory protein transport, but when introduced before the pulse it decreases the transfer of labeled proteins from the rough endoplasmic reticulum to the Golgi area, suppressing their temporary accumulation in the Golgi area before any alteration of this organelle is detectable. Moreover, colchicine inhibits protein release only from the secretory granules formed in its presence because the peroxidase discharge is diminished 1 h after colchicine addition, and the secretion of newly synthesized proteins is strongly inhibited only when colchicine is introduced before secretory granule formation. Morphometric studies show that there is a great increase of secondary lysosomes, related to crinophagy, as early as 40-50 min after colchicine is added. However, changes in lysosomal enzymatic activities remained biochemically undetectable. We conclude that: (a) the labile microtubular system does not seem indispensable for protein transport in the rough endoplasmic reticulum-Golgi area but may facilitate this step, perhaps by maintaining the spatial organization of this area; and (b) in the lacrimal gland, colchicine inhibits protein release not by acting on the steps of secretion following the secretory granule formation, but by acting chiefly on the steps preceding secretory granule formation, perhaps by making the secretory granules formed in its presence incapable of discharging their content.

scholarly journals AP-1 and clathrin are essential for secretory granule biogenesis in Drosophila

2011 ◽  
Vol 22 (12) ◽  
pp. 2094-2105 ◽  
Author(s):  
Jason Burgess ◽  
Miluska Jauregui ◽  
Julie Tan ◽  
Janet Rollins ◽  
Sylvie Lallet ◽  
...  
Keyword(s):  
Secretory Granule ◽  
Secretory Granules ◽  
Adaptor Protein ◽  
Fruit Fly ◽  
Biologically Active ◽  
Granule Formation ◽  
The Third ◽  
Larval Salivary Gland ◽  
Clathrin Adaptor ◽  
Golgi Network

 Regulated secretion of hormones, digestive enzymes, and other biologically active molecules requires the formation of secretory granules. Clathrin and the clathrin adaptor protein complex 1 (AP-1) are necessary for maturation of exocrine, endocrine, and neuroendocrine secretory granules. However, the initial steps of secretory granule biogenesis are only minimally understood. Powerful genetic approaches available in the fruit fly Drosophila melanogaster were used to investigate the molecular pathway for biogenesis of the mucin-containing “glue granules” that form within epithelial cells of the third-instar larval salivary gland. Clathrin and AP-1 colocalize at the trans-Golgi network (TGN) and clathrin recruitment requires AP-1. Furthermore, clathrin and AP-1 colocalize with secretory cargo at the TGN and on immature granules. Finally, loss of clathrin or AP-1 leads to a profound block in secretory granule formation. These findings establish a novel role for AP-1– and clathrin-dependent trafficking in the biogenesis of mucin-containing secretory granules.

scholarly journals Synaptotagmin IV is necessary for the maturation of secretory granules in PC12 cells

2006 ◽  
Vol 173 (2) ◽  
pp. 241-251 ◽  
Author(s):  
Malika Ahras ◽  
Grant P. Otto ◽  
Sharon A. Tooze
Keyword(s):  
Pc12 Cells ◽  
Secretory Granules ◽  
Granule Formation ◽  
Synaptotagmin Iv ◽  
Prohormone Convertase 2 ◽  
Granule Maturation ◽  
Golgi Network ◽  
Interfering Rna

In neuroendocrine PC12 cells, immature secretory granules (ISGs) mature through homotypic fusion and membrane remodeling. We present evidence that the ISG-localized synaptotagmin IV (Syt IV) is involved in ISG maturation. Using an in vitro homotypic fusion assay, we show that the cytoplasmic domain (CD) of Syt IV, but not of Syt I, VII, or IX, inhibits ISG homotypic fusion. Moreover, Syt IV CD binds specifically to ISGs and not to mature secretory granules (MSGs), and Syt IV binds to syntaxin 6, a SNARE protein that is involved in ISG maturation. ISG homotypic fusion was inhibited in vivo by small interfering RNA–mediated depletion of Syt IV. Furthermore, the Syt IV CD, as well as Syt IV depletion, reduces secretogranin II (SgII) processing by prohormone convertase 2 (PC2). PC2 is found mostly in the proform, suggesting that activation of PC2 is also inhibited. Granule formation, and the sorting of SgII and PC2 from the trans-Golgi network into ISGs and MSGs, however, is not affected. We conclude that Syt IV is an essential component for secretory granule maturation.

scholarly journals HID-1 is required for homotypic fusion of immature secretory granules during maturation

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Wen Du ◽  
Maoge Zhou ◽  
Wei Zhao ◽  
Dongwan Cheng ◽  
Lifen Wang ◽  
...  
Keyword(s):  
Secretory Granule ◽  
Molecular Mechanisms ◽  
Secretory Granules ◽  
Three Dimensional ◽  
Conditional Knockout ◽  
Active Peptides ◽  
Early Maturation ◽  
Proinsulin Processing ◽  
Granule Maturation ◽  
Golgi Network

Secretory granules, also known as dense core vesicles, are generated at the trans-Golgi network and undergo several maturation steps, including homotypic fusion of immature secretory granules (ISGs) and processing of prehormones to yield active peptides. The molecular mechanisms governing secretory granule maturation are largely unknown. Here, we investigate a highly conserved protein named HID-1 in a mouse model. A conditional knockout of HID-1 in pancreatic β cells leads to glucose intolerance and a remarkable increase in the serum proinsulin/insulin ratio caused by defective proinsulin processing. Large volume three-dimensional electron microscopy and immunofluorescence imaging reveal that ISGs are much more abundant in the absence of HID-1. We further demonstrate that HID-1 deficiency prevented secretory granule maturation by blocking homotypic fusion of immature secretory granules. Our data identify a novel player during the early maturation of immature secretory granules.

scholarly journals Golgi apparatus, GERL, and secretory granule formation within neurons of the hypothalamo-neurohypophysial system of control and hyperosmotically stressed mice.

1981 ◽  
Vol 90 (2) ◽  
pp. 474-484 ◽  
Author(s):  
R D Broadwell ◽  
C Oliver
Keyword(s):  
Golgi Apparatus ◽  
Secretory Granule ◽  
Supraoptic Nucleus ◽  
Salt Water ◽  
Secretory Granules ◽  
Hyperosmotic Stress ◽  
Granule Formation ◽  
Smooth Membrane ◽  
Secondary Lysosomes ◽  
The Relationship

The vasopressin-producing neurons of the hypothalamo-neurohypophysial system are a particularly good model with which to consider the relationship between the Golgi apparatus nd GERL and their roles in secretory granule production because these neurons increase their synthesis and secretion of vasopressin in response to hyperosmotic stress. Enzyme cytochemical techniques for acid phosphatase (AcPase) and thiamine pyrophosphatase (TPPase) activities were used to distinguish GERL from the Golgi apparatus in cell bodies of the supraoptic nucleus from normal mice, mice hyperosmotically stressed by drinking 2% salt water, and mice allowed to recover for 5-10 d from hyperosmotic stress. In nonincubated preparations of control supraoptic perikarya, immature secretory granules at the trans face of the Golgi apparatus were frequently attached to a narrow, smooth membrane cisterna identified as GERL. Secretory granules were occasionally seen attached to Golgi saccules. TPPase activity was present in one or two of the trans Golgi saccules; AcPase activity appeared in GERL and attached immature secretory granules, rarely in the trans Golgi saccules, and in secondary lysosomes. As a result of hyperosmotic stress, the Golgi apparatus hypertrophied, and secretory granules formed from all Golgi saccules and GERL. Little or no AcPase activity could be demonstrated in GERL, whereas all Golgi saccules and GERL-like cisternae were TPPase positive. During recovery, AcPase activity in GERL returned to normal; however, the elevated TPPase activity and secretory granule formation seen in GERL-like cisternae and all Golgi saccules during hyperosmotic stress persisted. These results suggest that under normal conditions GERL is the predominant site for the secretory granule formation, but during hyperosmotic stress, the Golgi saccules assume increased importance in this function. The observed cytochemical modulations in Golgi saccules and GERL suggest that GERL is structurally and functionally related to the Golgi saccules.

scholarly journals Functional Amyloids As Natural Storage of Peptide Hormones in Pituitary Secretory Granules

Science ◽  
2009 ◽  
Vol 325 (5938) ◽  
pp. 328-332 ◽  
Author(s):  
S. K. Maji ◽  
M. H. Perrin ◽  
M. R. Sawaya ◽  
S. Jessberger ◽  
K. Vadodaria ◽  
...  
Keyword(s):  
Secretory Granules ◽  
Peptide Hormones ◽  
Functional Amyloids

scholarly journals Expression of Regulated Secretory Proteins Is Sufficient to Generate Granule-like Structures in Constitutively Secreting Cells

2004 ◽  
Vol 279 (19) ◽  
pp. 20242-20249 ◽  
Author(s):  
Nicole Beuret ◽  
Hansruedi Stettler ◽  
Anja Renold ◽  
Jonas Rutishauser ◽  
Martin Spiess
Keyword(s):  
Protease Inhibitor ◽  
Secretory Granules ◽  
Secretory Proteins ◽  
Ionophore A23187 ◽  
Cell Periphery ◽  
Chromogranin B ◽  
Granule Formation ◽  
Trans Golgi Network ◽  
Secretogranin Ii ◽  
Golgi Network

The formation of secretory granules and regulated secretion are generally assumed to occur only in specialized endocrine, neuronal, or exocrine cells. We discovered that regulated secretory proteins such as the hormone precursors pro-vasopressin, pro-oxytocin, and pro-opiomelanocortin, as well as the granins secretogranin II and chromogranin B but not the constitutive secretory protein α1-protease inhibitor, accumulate in granular structures at the Golgi and in the cell periphery in transfected COS-1 fibroblast cells. The accumulations were observed in 30–70% of the transfected cells expressing the pro-hormones and for virtually all of the cells expressing the granins. Similar structures were also generated in other cell lines believed to be lacking a regulated secretory pathway. The accumulations resembled secretory granules morphologically in immunofluorescence and electron microscopy. They were devoid of markers of the endoplasmic reticulum, endosomes, and lysosomes but in part stained positive for the trans-Golgi network marker TGN46, consistent with their formation at the trans-Golgi network. When different regulated proteins were coexpressed, they were frequently found in the same granules, whereas α1-protease inhibitor could not be detected in accumulations formed by secretogranin II, demonstrating segregation of regulated from constitutive secretory proteins. In pulse-chase experiments, significant intracellular storage of secretogranin II and chromogranin B was observed and secretion of retained secretogranin II was stimulated with the calcium ionophore A23187. The results suggest that expression of regulated cargo proteins is sufficient to generate structures that resemble secretory granules in the background of constitutively secreting cells, supporting earlier proposals on the mechanism of granule formation.

Molecular chaperones in pancreatic tissue: the presence of cpn10, cpn60 and hsp70 in distinct compartments along the secretory pathway of the acinar cells

1994 ◽  
Vol 107 (3) ◽  
pp. 539-549 ◽  
Author(s):  
C.S. Velez-Granell ◽  
A.E. Arias ◽  
J.A. Torres-Ruiz ◽  
M. Bendayan
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Secretory Pathway ◽  
Secretory Granules ◽  
Acinar Cells ◽  
Pancreatic Tissue ◽  
Secretory Proteins ◽  
Trans Golgi Network ◽  
Hsp70 Protein ◽  
Golgi Network

Three chaperones, the chaperonins cpn10 and cpn60, and the hsp70 protein, were revealed by immunochemistry and cytochemistry in pancreatic rat acinar cells. Western immunoblotting analysis of rat pancreas homogenates has shown that antibodies against cpn10, cpn60 and hsp70 protein recognize single protein bands of 25 kDa, 60 kDa and 70 kDa, respectively. Single bands for the cpn10 and cpn60 were also detected in pancreatic juice. Immunofluorescence studies on rat pancreatic tissue revealed a strong positive signal in the apical region of the acinar cells for cpn10 and cpn60, while an immunoreaction was detected at the juxtanuclear Golgi region with the anti-hsp70 antibody. Immunocytochemical gold labeling confirmed the presence of these three chaperones in distinct cell compartments of pancreatic acinar cells. Chaperonin 10 and cpn60 were located in the endoplasmic reticulum, Golgi apparatus, condensing vacuoles and secretory granules. Interestingly, the labeling for both cpn10 and cpn60 followed the increasing concentration gradient of secretory proteins along the RER-Golgi-granule secretory pathway. On the contrary, the labeling for hsp70 was mainly concentrated in the endoplasmic reticulum and the Golgi apparatus. In the latter, the hsp70 was found to be primary located in the trans-most cisternae and to colocalize with acid phosphatase in the trans-Golgi network. The three chaperones were also present in mitochondria. In view of the role played by the chaperones in the proper folding, sorting and aggregation of proteins, we postulate that hsp70 assists the adequate sorting and packaging of proteins from the ER to the trans-Golgi network while cpn10 and cpn60 play key roles in the proper packaging and aggregation of secretory proteins as well as, most probably, in the prevention of early enzyme activation in secretory granules.

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