Polyamine-dependent alterations in the structure of microfilaments, golgi apparatus, endoplasmic reticulum, and proteoglycan synthesis in BHK cells

Abstract

The activity of ornithine decarboxylase, the key enzyme in the synthesis of polyamines, is essential for proliferation and differentiation of all living cells. Two inhibitors of ornithine decarboxylase, alpha-difluoromethylornithine (DFMO) and 1-aminooxy-3-aminopropane (APA), caused swelling of endoplasmic reticulum (ER) and medial and trans Golgi cisternae, and the disappearance of stress fibers, as visualized by staining with fluorescent concanavalin A (ConA), C6-NBD-ceramide or wheat germ agglutinin (WGA), and phalloidin, respectively. In contrast, the pattern of microtubules, stained with a beta-tubulin antibody, was not affected. Rough ER seemed to be especially affected in polyamine deprivation forming whorls and involutions, which were observed by transmission electron microscopy. Since ER and Golgi apparatus are vital parts of the glycosylation and secretory machinery of the cell, we tested the ability of these structurally altered cell organelles to synthesize proteoglycans using [3H]glucosamine and [35S]sulfate as precursors. The total incorporation rate into proteoglycans and hyaluronan was not reduced in polyamine-deprived cells, suggesting that the total glycosylation capacity of cells was not affected. However, the synthesis of a high molecular weight proteoglycan containing chondroitin and keratan sulfate was completely inhibited. The remodeling of cytoskeleton and rough endoplasmic reticulum in polyamine deprivation may perturb the synthesis and secretion of the components of membrane skeleton and of the extracellular matrix, e.g., proteoglycans. Rough ER and cytoskeleton may be the targets where polyamines affect cell proliferation and differentiation.

A Modified Tripeptide Motif of RS1 (RSC1A1) Down-Regulates Exocytotic Pathways of Human Na+-d-glucose Cotransporters SGLT1, SGLT2, and Glucose Sensor SGLT3 in the Presence of Glucose

“…Because RS1 and SGLT1 have been colocalized at the TGN (Korn et al, 2001) and antizyme inhibitor 2, which regulates vesicle trafficking via activation of ODC, has been also localized at the TGN (Parkkinen et al, 1997;Kanerva et al, 2010), we hypothesized that the posttranslational downregulation of SGLT1 by hRS1-Reg(S20E) and QEP occurs at the TGN. Because glucose decreases the dissociation constant for binding of hRS1(S20E) to ODC and the IC 50 values for inhibition of ODC by hRS1-Reg(S20E) or QEP (Chintalapati et al, 2016) (Fig.…”

Polyamine Metabolism and Oxidative Protein Folding in the ER as ROS-Producing Systems Neglected in Virology

“…In the current literature, polyamine metabolism and oxidative protein folding in the ER are still being considered as separate events, even though tight interlinks have been reported between them. It has been known for a long time that polyamine depletion, resulting from their inhibited biosynthesis, causes swelling of ER [ 247 ]. Prunotto et al provided evidence for increased expression of the classical UPR markers Grp78 and Grp94 in MDCK cells treated with profibrotic transforming growth factor β1 (TGFβ1) and DMFO, an inhibitor of polyamine biosynthesis, compared to TGFβ1-treated cells [ 248 ].…”

Acute Putrescine Supplementation with Schwann Cell Implantation Improves Sensory and Serotonergic Axon Growth and Functional Recovery in Spinal Cord Injured Rats

“…In addition to mediating cell migration and proliferation, putrescine and other downstream polyamines have also been shown to promote cell survival. Deficiencies in putrescine levels cause swelling of the endoplasmic reticulum and Golgi bodies, as well as the disappearance of stress fibers, all of which are hallmarks associated with necrosis [ 37 ]. Intracellular polyamines can alter ion transport, either blocking K + channels to prevent neuron excitotoxicity or promoting Ca 2+ influxes [ 38 , 39 ].…”