Biosynthesis and processing of pro‐C3, a precursor of the third component of complement in rat hepatocytes: effect of secretion‐blocking agents

Misumi, Yoshio; Takami, Noboru; Ikehara, Yukio

doi:10.1016/0014-5793(84)80570-0

Cited by 17 publications

(4 citation statements)

References 22 publications

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“…2 shows the effect of amines on the proteolytic processing of C3. As previously reported [23], C3 is synthesized as a single polypeptide chain (pro-C3) with Mr 180000 in rat hepatocytes (Fig. 2, lane 1), and proteolytically converted to the a (Mr 115000) and , (Mr 65 000) subunits, which are secreted into the medium (lane 2).…”

Section: Resultssupporting

confidence: 69%

Effects of weakly basic amines on proteolytic processing and terminal glycosylation of secretory proteins in cultured rat hepatocytes

Oda¹,

Koriyama²,

Yamada³

et al. 1986

Biochemical Journal

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We examined the effects of weakly basic amines on the secretion and post-translational modifications of secretory proteins in cultured rat hepatocytes. Weakly basic amines such as methylamine, chloroquine and NH4Cl strongly inhibited not only protein secretion, but also the proteolytic conversion of a proform of complement C3, allowing the precursor to be released into the medium. The amines, however, had no effect on the proteolytic conversion of prohaptoglobin into its subunits. Since available evidence indicates that the conversion of pro-C3 occurs at the Golgi complex while that of prohaptoglobin takes place in the endoplasmic reticulum, it is most likely that the weak bases specifically affect the proteolytic event occurring at the Golgi complex. Electron microscopic observations confirmed that the amines caused morphological changes of the Golgi complex, consisting of dilated cisternae and swollen vacuoles. When the glycosylation of alpha 1-protease inhibitor and haptoglobin was examined, it was found that the amines caused a marked accumulation in the cells of both glycoproteins corresponding to the mature secreted forms. Neuraminidase digestion demonstrated that the glycoproteins accumulating in response to the amines had acquired terminal sialic acid. The results indicate that the amines do not significantly affect terminal glycosylation, in contrast with their definite effect on proteolytic processing, despite the fact that both modifications take place in the Golgi complex.

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Section: Resultssupporting

confidence: 69%

Effects of weakly basic amines on proteolytic processing and terminal glycosylation of secretory proteins in cultured rat hepatocytes

Oda¹,

Koriyama²,

Yamada³

et al. 1986

Biochemical Journal

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“…A similar pattern of C3 processing was observed in primary hepatocytes cultured in starvation or in a nutrient-rich media and the abundance of a band migrating at around 180 kDa was increased upon nutrient addition (Figure 5d). In line with a previous report, 31 we were unable to detect mature C3 in total hepatocyte extracts, which may indicate that isolated primary hepatocytes have a reduced capacity to store mature C3 prior to secretion. Expression of C3 at the RNA level was also not affected by our experimental conditions (Supplementary Figure S13B), suggesting that translation of pro-C3 might be enhanced under nutrient-rich conditions.…”

Section: Resultssupporting

confidence: 92%

Liver ubiquitome uncovers nutrient-stress-mediated trafficking and secretion of complement C3

Magliarelli¹,

Matondo²,

Mészáros³

et al. 2016

Cell Death Dis

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Adaptation to changes in nutrient availability is crucial for cells and organisms. Posttranslational modifications of signaling proteins are very dynamic and are therefore key to promptly respond to nutrient deprivation or overload. Herein we screened for ubiquitylation of proteins in the livers of fasted and refed mice using a comprehensive systemic proteomic approach. Among 1641 identified proteins, 117 were differentially ubiquitylated upon fasting or refeeding. Endoplasmic reticulum (ER) and secretory proteins were enriched in the livers of refed mice in part owing to an ER-stress-mediated response engaging retro-translocation and ubiquitylation of proteins from the ER. Complement C3, an innate immune factor, emerged as the most prominent ER-related hit of our screen. Accordingly, we found that secretion of C3 from the liver and primary hepatocytes as well as its dynamic trafficking are nutrient dependent. Finally, obese mice with a chronic nutrient overload show constitutive trafficking of C3 in the livers despite acute changes in nutrition, which goes in line with increased C3 levels and low-grade inflammation reported for obese patients. Our study thus suggests that nutrient sensing in the liver is coupled to release of C3 and potentially its metabolic and inflammatory functions.

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“…7). Colchicine treatment caused accumulation of processed C3 in rat hepatocytes [33], thus implicating microtubules in the transport of C3containing secretory vesicles to the plasma membrane. Normal proC3 that is retained in the ER due to disruption of the Golgi structure and function (Fig.…”

Section: Discussionmentioning

confidence: 93%

Distinction between processing of normal and mutant complement C3 within human skin fibroblasts

et al. 1999

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Inherited C3 deficiency may result from mutations in the C3 gene affecting transcription or translation (type I deficiency). We described a type II C3 deficiency caused by a mutation yielding an abnormal non-secreted C3. The post-translational processing of mutant and normal C3 was analyzed in fibroblasts grown from skin biopsies. Mutant C3 is located mainly in the endoplasmic reticulum (ER), whereas normal C3 is seen evenly distributed throughout the cytoplasm. Most of the mutant C3 is degraded within the cell, and only a small fraction (around 8%) is secreted after 20 h chase. Processing of C3 at 19 degrees C was reduced in normal fibroblasts but completely blocked in mutant fibroblasts. ATP depletion blocked processing of normal proC3 to C3. In contrast, the mutant proC3 was partly degraded in ATP-depleted cells, yet its complete degradation and secretion were blocked. Intracellular degradation of the mutant C3 was not inhibited by NH4Cl, thus excluding cleavage within lysosomes. These results demonstrate that the type II mutant C3 studied here is retained in the ER probably by a quality contol machinery that identifies abnormal protein folding. Consequently, it is destined to undergo a two-step intracellular degradation; an initial ATP-independent step followed by an ATP-dependent step.

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Biosynthesis and processing of pro‐C3, a precursor of the third component of complement in rat hepatocytes: effect of secretion‐blocking agents

Cited by 17 publications

References 22 publications

Effects of weakly basic amines on proteolytic processing and terminal glycosylation of secretory proteins in cultured rat hepatocytes

Effects of weakly basic amines on proteolytic processing and terminal glycosylation of secretory proteins in cultured rat hepatocytes

Liver ubiquitome uncovers nutrient-stress-mediated trafficking and secretion of complement C3

Distinction between processing of normal and mutant complement C3 within human skin fibroblasts

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