Accommodation of protein synthesis to chronic deprivation of intracellular sequestered calcium. A putative role for GRP78

Brostrom, Margaret A.; Cade, Christina; Prostko, C R; Gmitter-Yellen, D; Brostrom, Charles O.

doi:10.1016/s0021-9258(17)30536-7

Cited by 57 publications

(6 citation statements)

References 33 publications

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“…The Ca z+ chelator BAPTA used as the acetoxymethyl ester form would be expected to be taken up, cleaved, and the free BAPTA chelate cytosolic Call. BAPTA-AM produced a marked inhibition of total synthesis consistent with the findings that depletion of cytosolic Cal+ inhibits protein synthesis (Brostrom et al ., 1990) and the early stages of the secretory pathway (Balch, 1989), and increases protein degradation in the ER (Wileman et al ., 1991). The variability of the results with BAPTAAM due to the low levels of counts incorporated made it impossible to reliably determine the effect of this chelator on the extent of protein secretion.…”

Section: Resultssupporting

confidence: 88%

“…In this study we found, using a continuous labeling protocol, that a prolonged exposure to ionomycin produced a substantial inhibition of protein synthesis . Such a phenomenon has previously been reported for other cell types (Brostrom et al, 1990;Wileman et al, 1991) . Under these conditions ionomycin still increases the extent of secretion but problems of interpretation were avoided by the use of a pulse-chase protocol in later experiments .…”

Section: Discussionsupporting

confidence: 82%

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Proteins are secreted by both constitutive and regulated secretory pathways in lactating mouse mammary epithelial cells

Turner

Rennison

Handel

et al. 1992

The Journal of Cell Biology

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Abstract. Lactating mammary epithelial cells secrete high levels of caseins and other milk proteins. The extent to which protein secretion from these cells occurs in a regulated fashion was examined in experiments on secretory acini isolated from the mammary glands of lactating mice at 10 d postpartum . Protein synthesis and secretion were assayed by following the incorporation or release, respectively, of [35S]methionine-labeled TCAprecipitable protein. The isolated cells incorporated [35S]methionine into protein linearly for at least 5 h with no discernible lag period. In contrast, protein secretion was only detectable after a lag of -1 h, consistent with exocytotic secretion of proteins immediately after passage through the secretory pathway and package into secretory vesicles . The extent of protein secretion was unaffected by the phorbol ester PMA, 8-bromo-CAMP, or 8-bromo-cGMP but was doubled by the Call ionophore ionomycin . In a pulse-label protocol in which proteins were prelabeled for 1 h before P ROTE1N secretion by exocytosis occurs in many different cell types and is the mechanism involved in the secretion ofa wide range of molecules. Exocytotic secretion occurs either immediately after synthesis and packaging of proteins into secretory vesicles (constitutive exocytosis) or, following variable periods ofstorage in secretory vesicles or granules, in response to cell activation (regulated exocytosis) (Burgess and Kelly, 1987). Lactating mammary epithelial cells actively secrete large quantities of caseins and other milk proteins by an exocytotic mechanism (Franke et al., 1976;Linzell and Peaker, 1971;Saacke and Heald, 1974) in an apparently constitutive fashion . The possibility that mammary epithelial cells secrete caseins via a regulated secretory pathway has not been rigorously examined and much is still to be learned about the cell biology of secretion from this cell type.The signaling pathways involved in the differentiation of mammary epithelial cells to a secretory phenotype have been examined in detail, but less is known about the factors that may regulate exocytosis in lactating cells . Relatively little work has been carried out in recent years on the effect of sec-

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Section: Resultssupporting

confidence: 88%

Section: Discussionsupporting

confidence: 82%

Proteins are secreted by both constitutive and regulated secretory pathways in lactating mouse mammary epithelial cells

Turner

Rennison

Handel

et al. 1992

The Journal of Cell Biology

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“…In the control state, protein synthesis is closely affected by levels of ER Ca# + stores (reviewed in [19]). Under conditions associated with disturbance of ER Ca# + homoeostasis or an impairment of ER-resident protein folding or processing reactions, the initiation process of protein synthesis is suppressed, as indicated by a phosphorylation of eIF-2α and a disaggregation of polyribosomes [20][21][22]. Depletion of ER Ca# + stores causes a slight transient increase in cytoplasmic Ca# + activity [16], which may also affect protein synthesis.…”

Section: Discussionmentioning

confidence: 99%

Response of neurons to an irreversible inhibition of endoplasmic reticulum Ca2+-ATPase: relationship between global protein synthesis and expression and translation of individual genes

et al. 2001

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In the physiological state, there appears to be a regulatory link between endoplasmic reticulum (ER) Ca(2+) homoeostasis and the initiation of neuronal protein synthesis. Exposing neuronal cell cultures to thapsigargin (Tg), an irreversible inhibitor of sarcoplasmic/ER Ca(2+)-ATPase (SERCA), induced an almost complete suppression of protein synthesis, which recovered to approx. 60% of control 24 h after Tg exposure. This is an experimental model where the regulatory link between the initiation of protein synthesis and ER Ca(2+) homoeostasis recovers, despite an irreversible suppression of SERCA activity [Doutheil, Treiman, Oschlies and Paschen (1999) Cell Calcium 25, 419--428]. The model was used to investigate the relationship between transcription and translation of various stress genes that respond to conditions causing graded suppression of protein synthesis. Expression patterns revealed three groups of genes. The mRNA levels of genes responding to conditions of ER stress (grp78, grp94, gadd34 and gadd153) were increased up to 200-fold after Tg exposure, whereas those coding for ER-resident proteins (SERCA 2b and Bcl-2) were increased up to 6-fold in treated cultures, and those coding for cytoplasmic proteins (heat-shock protein 70 and p67) were increased only 2--4-fold. Analysis of translation of these mRNAs suggests an imbalance in the synthesis of apoptosis-inducing (GADD153) and tolerance-activating (GRP78 and Bcl-2) proteins after blocking of the ER Ca(2+) pump. The observation that the relationship between Tg-induced changes in mRNA and protein levels varied considerably for the various genes studied implies that translation of the respective transcripts is differently regulated under conditions causing graded suppression of global protein synthesis. Detailed analysis of the response of neuronal cells to transient disturbance of ER Ca(2+) homoeostasis may help to elucidate the mechanisms underlying neuronal cell injury in those neurological disorders in which an impairment of ER function is thought to contribute to the pathological process of deterioration.

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“…The GRP94 and GRP78 are also present in the sarcoplasmic reticulum vesicles of cardiac and skeletal muscles, another organelle known to contain high levels of Ca 2 + (Milner et al, 1992;Volpe et al, 1992;Cala and Jones, 1994). Thus, as low affinity but high capacity Ca 2 +binding proteins, GRPs may play significant roles in protein trafficking (Gething and Sambrook, 1992) and intracellular Ca 2 + homeostasis (Brostrom et al, 1990).…”

Section: Generation Of a Mammalian Cell Line Deficient In Glucoseregulated Protein Stress Induction Through Targeted Ribozymementioning

confidence: 99%

Generation of a Mammalian Cell Line Deficient in Glucose-regulated Protein Stress Induction through Targeted Ribozyme Driven by a Stress-inducible Promoter

Little

Lee

1995

Journal of Biological Chemistry

100

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Cyclic ADP-ribose (cADPR) is emerging as an endogenous regulator of Ca2+-induced Ca2+ release (CICR), and we have recently demonstrated that its action is mediated by calmodulin (CaM) (Lee, H. C., Aarhus, R., Graeff, R., Gurnack, M. E., and Walseth, T. F. (1994) Nature 370, 307-309). In this study we show by immunoblot analyses that the protein factor in sea urchin eggs responsible for conferring cADPR sensitivity to egg microsomes was CaM. This was further supported by the fact that bovine CaM was equally effective as the egg factor. In contrast, plant CaM was only partially active even at 10-20-fold higher concentrations. This exquisite specificity was also shown by binding studies using 125I-labeled bovine CaM. The effectiveness of various CaMs (bovine > spinach > wheat germ) in competing for the binding sites was identical to their potency in conferring cADPR sensitivity to the microsomes. A comparison between bovine and wheat germ CaM in competing for the sites suggests only 10-14% of the total binding was crucial for the activity. Depending on the CaM concentration, the sensitivity of the microsomes to cADPR could be changed by several orders of magnitude. The requirement for CaM could be alleviated by raising the divalent cation concentration with Sr2+. Results showed that CaM, cADPR, and caffeine all act synergistically to increase the divalent cation sensitivity of the CICR mechanism. The combined action of any of the three agonists was sufficient to sensitize the mechanism so much that even the nanomolar concentration of ambient Ca2+ was enough to activate the release. Unlike the CICR mechanism, the microsomal inositol 1,4,5-trisphosphate-sensitive Ca2+ release showed no dependence on CaM. Using an antagonist of CaM, W7, it was demonstrated that the cADPR-but not the inositol 1,4,5-trisphosphate-dependent release mechanism could be blocked in live sea urchin eggs. These results indicate cADPR can function as a physiological modulator of CICR and, together with CaM, can alter the sensitivity of the release mechanism to divalent cation by several orders of magnitude.

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Accommodation of protein synthesis to chronic deprivation of intracellular sequestered calcium. A putative role for GRP78

Cited by 57 publications

References 33 publications

Proteins are secreted by both constitutive and regulated secretory pathways in lactating mouse mammary epithelial cells

Proteins are secreted by both constitutive and regulated secretory pathways in lactating mouse mammary epithelial cells

Response of neurons to an irreversible inhibition of endoplasmic reticulum Ca2+-ATPase: relationship between global protein synthesis and expression and translation of individual genes

Generation of a Mammalian Cell Line Deficient in Glucose-regulated Protein Stress Induction through Targeted Ribozyme Driven by a Stress-inducible Promoter

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