scholarly journals A quantitative study of the Golgi retention of glycosyltransferases

2021 ◽  
Author(s):  
Xiuping Sun ◽  
Bing Chen ◽  
Zhiwei Song ◽  
Lei Lu
Keyword(s):  
Plasma Membrane ◽  
Transferrin Receptor ◽  
Tumor Necrosis ◽  
Tumor Necrosis Factor Α ◽  
Transmembrane Domain ◽  
Tail Length ◽  
Golgi Retention ◽  
Factor Α ◽  
Export Signal ◽  
Necrosis Factor

ABSTRACTHow Golgi glycosyltransferases and glycosidases (hereafter glycosyltransferases) localize to the Golgi is still unclear. Here, we first investigated the post-Golgi trafficking of glycosyltransferases. We found that glycosyltransferases can escape the Golgi to the plasma membrane, where they are subsequently endocytosed to the endolysosome. Post-Golgi glycosyltransferases are probably degraded by the ecto-domain shedding. We discovered that most glycosyltransferases are not retrieved from post-Golgi sites, indicating that retention but not retrieval should be the main mechanism for their Golgi localization. We proposed to use the Golgi residence time to study the Golgi retention of glycosyltransferases quantitatively and systematically. Various chimeras between ST6GAL1 and either transferrin receptor or tumor necrosis factor α quantitatively revealed the contributions of three regions of ST6GAL1, namely the N-terminal cytosolic tail, transmembrane domain and ecto-domain, to the Golgi retention. We found that each of the three regions is sufficient to produce a retention in an additive manner. The N-terminal cytosolic tail length negatively affects the Golgi retention of ST6GAL1, similar to what is known of the transmembrane domain. Therefore, long N-terminal cytosolic tail and transmembrane domain can be a Golgi export signal for transmembrane secretory cargos.

scholarly journals A quantitative study of the Golgi retention of glycosyltransferases

2021 ◽  
Author(s):  
Xiuping Sun ◽  
Mahajan Divyanshu ◽  
Bing Chen ◽  
Zhiwei Song ◽  
Lei Lu
Keyword(s):  
Transferrin Receptor ◽  
Tumor Necrosis ◽  
Transmembrane Domain ◽  
Tail Length ◽  
Ectodomain Shedding ◽  
Primary Mechanism ◽  
Golgi Retention ◽  
Factor Α ◽  
Export Signal ◽  
Necrosis Factor

How Golgi glycosyltransferases and glycosidases (hereafter glycosyltransferases) localize to the Golgi is still unclear. Here, we first investigated the post-Golgi trafficking of glycosyltransferases. We found that glycosyltransferases can escape the Golgi to the plasma membrane, where they are subsequently endocytosed to the endolysosome. Post-Golgi glycosyltransferases are probably degraded by the ectodomain shedding. We discovered that most glycosyltransferases are not retrieved from post-Golgi sites, indicating that retention but not retrieval should be the primary mechanism for their Golgi localization. We proposed to use the Golgi residence time to quantitatively and systematically study Golgi retention of glycosyltransferases. Various swapping chimeras between ST6GAL1 and either transferrin receptor or tumor necrosis factor α quantitatively revealed the contributions of three regions of ST6GAL1, namely the N-terminal cytosolic tail, transmembrane domain, and ectodomain, to Golgi retention. We found that each of the three regions is sufficient to produce retention in an additive manner. The N-terminal cytosolic tail length negatively affects the Golgi retention of ST6GAL1, similar to the effect of the transmembrane domain. Therefore, the long N-terminal cytosolic tail and transmembrane domain can be a Golgi export signal for transmembrane secretory cargos.

Tumor necrosis factor α induces a caspase-independent death pathway in human neutrophils

Blood ◽  
2003 ◽  
Vol 101 (5) ◽  
pp. 1987-1995 ◽  
Author(s):  
Nikolai A. Maianski ◽  
Dirk Roos ◽  
Taco W. Kuijpers
Keyword(s):  
Cell Death ◽  
Plasma Membrane ◽  
Tumor Necrosis Factor ◽  
Tumor Necrosis ◽  
Tumor Necrosis Factor Α ◽  
Human Neutrophils ◽  
Dna Laddering ◽  
Tnf Α ◽  
Factor Α ◽  
Necrosis Factor

Tumor necrosis factor α (TNF-α) is a cytokine with multiple roles in the immune system, including the induction and potentiation of cellular functions in neutrophils (PMNs). TNF-α also induces apoptotic signals leading to the activation of several caspases, which are involved in different steps of the process of cell death. Inhibition of caspases usually increases cell survival. Here, we found that inhibition of caspases by the general caspase inhibitor zVAD-fmk did not prevent TNF-α–induced PMN death. After 6 hours of incubation, TNF-α alone caused PMN death with characteristic apoptotic features (typical morphologic changes, DNA laddering, external phosphatidyl serine [PS] exposure in the plasma membrane, Bax clustering and translocation to the mitochondria, and degradation of mitochondria), which coincided with activation of caspase-8 and caspase-3. However, in the presence of TNF-α, PMNs died even when caspases were completely inhibited. This type of cell death lacked nuclear features of apoptosis (ie, no DNA laddering but aberrant hyperlobulated nuclei without typical chromatin condensation) and demonstrated no Bax redistribution, but it did show mitochondria clustering and plasma membrane PS exposure. In contrast, Fas-triggered PMN apoptosis was completely blocked by zVAD-fmk. Experiments with scavengers of reactive oxygen species (ROS) and with inhibitors of mitochondrial respiration, with PMN-derived cytoplasts (which lack mitochondria) and with PMNs from patients with chronic granulomatous disease (which have impaired nicotinamide adenine dinucleotide phosphate [NADPH] oxidase) indicated that TNF-α/zVAD-fmk–induced cell death depends on mitochondria-derived ROS. Thus, TNF-α can induce a “classical,” caspase-dependent and a “nonclassical” caspase-independent cell death.

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