Adaptor Protein Ruk/CIN85 is Associated with a Subset of COPI-Coated Membranes of the Golgi Complex

The four members of the AP (adaptor protein) family are heterotetrameric cytosolic complexes that are involved in the intracellular trafficking of cargo proteins between different organelles. They interact with motifs present in the cytoplasmic tails of their specific cargo proteins at different intracellular locations. While AP-1, AP-2 and AP-3 have been investigated extensively, very few studies have focused on the fourth member, AP-4. In the present study, we report on the intracellular localization of AP-4 in the MDCK (Madin–Darby canine kidney) and MelJuSo cell lines after immunogold labelling of ultrathin cryosections. We find that AP-4 is localized mainly in the Golgi complex, as well as on endosomes and transport vesicles. Interestingly, we show for the first time that AP-4 is localized with the clathrin coat machinery in the Golgi complex and in the endocytic pathway. Furthermore, we find that AP-4 is localized with the CI-MPR (cation-independent mannose 6-phosphate receptor), but not with the transferrin receptor, LAMP-2 (lysosomal-associated membrane protein-2) or invariant chain. The difference in morphology between CI-MPR/AP-4-positive vesicles and CI-MPR/AP-1-positive vesicles raises the possibility that AP-4 acts at a location different from that of AP-1 in the intracellular trafficking pathway of CI-MPR.

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Vps41p Function in the Alkaline Phosphatase Pathway Requires Homo-oligomerization and Interaction with AP-3 through Two Distinct Domains

Molecular Biology of the Cell ◽

10.1091/mbc.12.1.37 ◽

2001 ◽

Vol 12 (1) ◽

pp. 37-51 ◽

Cited By ~ 66

Author(s):

Tamara Darsow ◽

David J. Katzmann ◽

Christopher R. Cowles ◽

Scott D. Emr

Keyword(s):

Alkaline Phosphatase ◽

Golgi Complex ◽

Protein Transport ◽

Adaptor Protein ◽

Accessory Proteins ◽

Sequencing Analysis ◽

Coat Proteins ◽

Membrane Recruitment ◽

Oligomeric Form ◽

New Alleles

Transport of proteins through the ALP (alkaline phosphatase) pathway to the vacuole requires the function of the AP-3 adaptor complex and Vps41p. However, unlike other adaptor protein–dependent pathways, the ALP pathway has not been shown to require additional accessory proteins or coat proteins, such as membrane recruitment factors or clathrin. Two independent genetic approaches have been used to identify new mutants that affect transport through the ALP pathway. These screens yielded new mutants in both VPS41 and the four AP-3 subunit genes. Two new VPS41 alleles exhibited phenotypes distinct from null mutants of VPS41, which are defective in vacuolar morphology and protein transport through both the ALP and CPY sorting pathways. The new alleles displayed severe ALP sorting defects, normal vacuolar morphology, and defects in ALP vesicle formation at the Golgi complex. Sequencing analysis of theseVPS41 alleles revealed mutations encoding amino acid changes in two distinct domains of Vps41p: a conserved N-terminal domain and a C-terminal clathrin heavy-chain repeat (CHCR) domain. We demonstrate that the N-terminus of Vps41p is required for binding to AP-3, whereas the C-terminal CHCR domain directs homo-oligomerization of Vps41p. These data indicate that a homo-oligomeric form of Vps41p is required for the formation of ALP containing vesicles at the Golgi complex via interactions with AP-3.

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Adaptor protein CD2AP and L-type lectin LMAN2 regulate exosome cargo protein trafficking through the Golgi complex.

Journal of Biological Chemistry ◽

10.1074/jbc.a116.729202 ◽

2017 ◽

Vol 292 (40) ◽

pp. 16523-16523 ◽

Cited By ~ 2

Author(s):

Sang-Ho Kwon ◽

Sekyung Oh ◽

Marisa Nacke ◽

Keith E. Mostov ◽

Joshua H. Lipschutz

Keyword(s):

Golgi Complex ◽

Protein Trafficking ◽

Adaptor Protein ◽

Cargo Protein

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The activity of Sac1 across ER–TGN contact sites requires the four-phosphate-adaptor-protein-1

The Journal of Cell Biology ◽

10.1083/jcb.201812021 ◽

2019 ◽

Vol 218 (3) ◽

pp. 783-797 ◽

Cited By ~ 22

Author(s):

Rossella Venditti ◽

Maria Chiara Masone ◽

Laura Rita Rega ◽

Giuseppe Di Tullio ◽

Michele Santoro ◽

...

Keyword(s):

Membrane Protein ◽

Phosphatase Activity ◽

Golgi Complex ◽

Adaptor Protein ◽

Contact Sites ◽

In Trans ◽

Phosphatidylinositol 4 ◽

Er Membrane

Phosphatidylinositol-4-phosphate (PI4P), a phosphoinositide with key roles in the Golgi complex, is made by Golgi-associated phosphatidylinositol-4 kinases and consumed by the 4-phosphatase Sac1 that, instead, is an ER membrane protein. Here, we show that the contact sites between the ER and the TGN (ERTGoCS) provide a spatial setting suitable for Sac1 to dephosphorylate PI4P at the TGN. The ERTGoCS, though necessary, are not sufficient for the phosphatase activity of Sac1 on TGN PI4P, since this needs the phosphatidyl-four-phosphate-adaptor-protein-1 (FAPP1). FAPP1 localizes at ERTGoCS, interacts with Sac1, and promotes its in-trans phosphatase activity in vitro. We envision that FAPP1, acting as a PI4P detector and adaptor, positions Sac1 close to TGN domains with elevated PI4P concentrations allowing PI4P consumption. Indeed, FAPP1 depletion induces an increase in TGN PI4P that leads to increased secretion of selected cargoes (e.g., ApoB100), indicating that FAPP1, by controlling PI4P levels, acts as a gatekeeper of Golgi exit.

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ACBD3 is required for FAPP2 transferring glucosylceramide through maintaining the Golgi integrity

Journal of Molecular Cell Biology ◽

10.1093/jmcb/mjy030 ◽

2018 ◽

Vol 11 (2) ◽

pp. 107-117 ◽

Cited By ~ 8

Author(s):

Jing Liao ◽

Yuxiang Guan ◽

Wei Chen ◽

Can Shi ◽

Dongdong Yao ◽

...

Keyword(s):

Golgi Complex ◽

Adaptor Protein ◽

Sphingolipid Metabolism ◽

Lipidomic Analysis ◽

Physiological Processes ◽

Molecular Machinery ◽

Golgi Fragmentation ◽

Acyl Coenzyme A ◽

Golgi Network ◽

Cell Signaling Pathways

Abstract Glycosphingolipid (GSL) metabolism is involved in various physiological processes, including all major cell signaling pathways, and its dysregulation is linked to some diseases. The four-phosphate adaptor protein FAPP2-mediated glucosylceramide (GlcCer) transport for complex GSL synthesis has been studied extensively. However, the molecular machinery of FAPP2 as a GlcCer-transferring protein remains poorly defined. Here, we identify a Golgi-resident protein, acyl-coenzyme A binding domain containing 3 (ACBD3), as an interacting partner of FAPP2. We find that ACBD3 knockdown leads to dramatic Golgi fragmentation, which subsequently causes FAPP2 dispersal throughout the cytoplasm and a decreased localization at trans-Golgi network. The further quantitative lipidomic analysis indicates that ACBD3 knockdown triggers abnormal sphingolipid metabolism. Interestingly, the expression of siRNA-resistant full-length ACBD3 can rescue these defects caused by ACBD3 knockdown. These data reveal critical roles for ACBD3 in maintaining the integrity of Golgi morphology and cellular sphingolipid homeostasis and establish the importance of the integrated Golgi complex for the transfer of GlcCer and complex GSL synthesis.

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Organisation in the Structure of the Cytoplasmic Ground Substance

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100070357 ◽

1978 ◽

Vol 36 (3) ◽

pp. 627-639

Author(s):

K.R. Porter

Keyword(s):

Endoplasmic Reticulum ◽

Golgi Complex ◽

Random Distribution ◽

Ground Substance ◽

The Matrix ◽

Cell Processes ◽

Cytoplasmic Ground Substance

Most types of cells are known from their structure and overall form to possess a characteristic organization. In some instances this is evident in the non-random disposition of organelles and such system subunits as cisternae of the endoplasmic reticulum or the Golgi complex. In others it appears in the distribution and orientation of cytoplasmic fibrils. And in yet others the organization finds expression in the non-random distribution and orientation of microtubules, especially as found in highly anisometric cells and cell processes. The impression is unavoidable that in none of these cases is the organization achieved without the involvement of the cytoplasmic ground substance (CGS) or matrix. This impression is based on the fact that a matrix is present and that in all instances these formed structures, whether membranelimited or filamentous, are suspended in it. In some well-known instances, as in arrays of microtubules which make up axonemes and axostyles, the matrix resolves itself into bridges (and spokes) between the microtubules, bridges which are in some cases very regularly disposed and uniform in size (Mcintosh, 1973; Bloodgood and Miller, 1974; Warner and Satir, 1974).

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Ultrastructural Aspects of Golgi Complex Function in Parathyroid Cells of Winter Frogs

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100073842 ◽

1973 ◽

Vol 31 ◽

pp. 680-681

Author(s):

William J. Dougherty

Keyword(s):

Golgi Complex ◽

Secretory Granules ◽

Complex Function ◽

Secretory Activity ◽

Secretory Proteins ◽

Perivascular Spaces ◽

Pituitary Cells ◽

Electron Microscopic ◽

Ca Ions ◽

Regulation Of Secretion

The regulation of secretion in exocrine and endocrine cells has long been of interest. Electron microscopic and other studies have demonstrated that secretory proteins synthesized on ribosomes are transported by the rough ER to the Golgi complex where they are concentrated into secretory granules. During active secretion, secretory granules fuse with the cell membrane, liberating and discharging their contents into the perivascular spaces. When secretory activity is suppressed in anterior pituitary cells, undischarged secretory granules may be degraded by lysosomes. In the parathyroid gland, evidence indicates that the level of blood Ca ions regulates both the production and release of parathormone. Thus, when serum Ca is low, synthesis and release of parathormone are both stimulated; when serum Ca is elevated, these processes are inhibited.

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Structures Resembling Striated Rootlets in Oocytes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100093870 ◽

1972 ◽

Vol 30 ◽

pp. 124-125

Author(s):

Valerie V. Ernst

Keyword(s):

Golgi Complex ◽

Fibrous Structure ◽

Oocyte Development ◽

The Cross

During the earliest stage of oocyte development in the limpet, Acmea scutum, Golgi complexes are small, few and randomly dispersed in the cytoplasm. As growth proceeds, the Golgi complexes increase in size and number and migrate to the periphery of the cell. At this time, fibrous structures resembling striated rootlets occur associated with the Golgi complexes. Only one fibrous structure appears to be associated with a Golgi complex.The fibers are periodically cross banded with an average of 4 dense fibrils and 6 lighter fibrils per period (Fig. 1). The cross fibrils have a center to center spacing of about 7 run which appears to be the same as that of the striated rootlets of the gill cilia in this animal.

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Demonstration of Secondary Lysosomes in Bovine Megakaryocytes and Platelets Using Acid Phosphatase Cytochemistry with Cerium as a Trapping Agent

Thrombosis and Haemostasis ◽

10.1055/s-0038-1645698 ◽

1990 ◽

Vol 63 (01) ◽

pp. 127-132 ◽

Cited By ~ 11

Author(s):

Michèle Ménard ◽

Kenneth M Meyers ◽

David J Prieur

Keyword(s):

Acid Phosphatase ◽

Electron Density ◽

Golgi Complex ◽

Initial Report ◽

Cerium Phosphate ◽

Virtual Absence ◽

Phosphatase Cytochemistry ◽

Secondary Lysosomes ◽

Trapping Agent

SummaryThe ultrastructure of lysosomes from bovine megakaryocytes (MK) and platelets was characterized using acid phosphatase cytochemistry with beta-glycerophosphate as substrate and cerium as a trapping agent. The technique was easily reproducible; cerium-phosphate precipitates were uniform, readily visualized, and there was a virtual absence of nonspecific reaction product. Acid phosphatase was localized in the trans aspect of the Golgi complex and/or granules of less than 50 nm to 650 nm diameters in MK at all stages of maturation. Forty percent of the MK lysosomes contained inclusions of variable shapes, sizes and electron-density and were classified as secondary lysosomes. Twenty-four percent of the platelet sections contained acid phosphatase-positive granules. Fifty-four percent of these were secondary lysosomes. This is the initial report demonstrating secondary lysosomes in either resting MK or platelets using acid phosphatase cytochemistry. These findings suggest that MK and platelet lysosomes have an intracellular function in resting MK and platelets.

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