Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.1.52 (PNGase F)
 1,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Breast tumor cell lines have been shown to secrete several distinct polypeptide growth factors, although conflicting results exist for the insulin-like growth factors (IGFs). In contrast a limited number of breast tumor cell lines have definitely been shown to secrete the high affinity IGF binding proteins (IGFBPs) that modify IGF actions. To characterize the types of IGFBPs that are secreted by breast tumor cell lines, conditioned medium was collected from seven separate tumor cell lines, three of which were estrogen receptor (ER) negative, and four of which were ER positive. All three of the ER negative cell lines, MDA-231, MDA-330, and HS578T, secreted binding proteins of 49,000 and 43,000 Mr (IGFBP-3) as well as 29,000 (IGFBP-1) and 24,000 Mr. In contrast, all four ER positive cell lines secreted 34,000 (IGFBP-2) or 24,000 Mr forms, and none secreted the 49,000 and 43,000 or 29,000 Mr forms. BT-20, a cell line that is positive for ER messenger RNA (mRNA) but negative for ER protein, secreted predominantly a 34,000 Mr protein. The amount of total IGFBP activity released in 24 h ranged between 0.4 and 5.6 nM equivalents of IGFBP-1, and there was no significant difference between the ER positive and negative cell lines. The MCF-7 cells that produced predominantly 34,000 and 24,000 Mr forms showed a 1.8-fold increase in IGFBP secretion after estrogen stimulation. Immunoblotting and a specific RIA for IGFBP-1 showed that only the ER negative lines MDA-330, MDA-231, and HS578T secreted this form. Northern blotting analysis for the mRNA encoding this protein showed that both MDA-330 and MDA-231 contained a single 1.6 kilobase mRNA species that hybridized with an IGFBP-1 complementary DNA (cDNA) probe. Immunoblotting analysis of the other cell lines showed that only the 34,000 Mr form secreted by the ER positive cell lines reacted with IGFBP-2 antisera. Exposure of the conditioned media from the three ER negative cell lines to N-glycanase revealed that the 49,000 and 43,000 Mr forms of IGFBP were glycosylated and therefore probably represent IGFBP-3. We conclude that ER negative cell lines secrete three forms of IGFBPs, IGFBP-1, IGFBP-3, and a 24,000 Mr form. In contrast, the ER positive cell lines secrete predominantly IGFBP-2 and the 24,000 Mr form but do not secrete IGFBP-3 or 1.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Insulin-like growth factor binding protein secretion by breast carcinoma cell lines: correlation with estrogen receptor status. 170 Nov 24

The deglycosylating enzyme, peptide:N-glycanase, acts on misfolded N-linked glycoproteins dislocated from the endoplasmic reticulum (ER) to the cytosol. Deglycosylation has been demonstrated to occur at the ER membrane and in the cytosol. However, the mechanism of PNGase association with the ER membrane was unclear, because PNGase lacked the necessary signal to facilitate its incorporation in the ER membrane, nor was it known to bind to an integral ER protein. Using HeLa cells, we have identified a membrane protein that associates with PNGase, thereby bringing it in close proximity to the ER and providing accessibility to dislocating glycoproteins. This protein, Derlin-1, has recently been shown to mediate retrotranslocation of misfolded glycoproteins. In this study we demonstrate that Derlin-1 interacts with the N-terminal domain of PNGase via its cytosolic C-terminus. Moreover, we find PNGase distributed in two populations; ER-associated and free in the cytosol, which suggests the deglycosylation process can proceed at either site depending on the glycoprotein substrate.
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PMID:The retrotranslocation protein Derlin-1 binds peptide:N-glycanase to the endoplasmic reticulum. 1605 2

The endoplasmic reticulum (ER) glycoprotein HMG-CoA reductase (HMGR) catalyzes the rate-limiting step in sterols biosynthesis. Mammalian HMGR is ubiquitinated and degraded by the proteasome when sterols accumulate in cells, representing the best example for metabolically controlled ER-associated degradation (ERAD). This regulated degradation involves the short-lived ER protein Insig-1. Here, we investigated the dislocation of these ERAD substrates to the cytosol en route to proteasomal degradation. We show that the tagged HMGR membrane region, HMG(350)-HA, the endogenous HMGR, and Insig-1-Myc, all polytopic membrane proteins, dislocate to the cytosol as intact full-length polypeptides. Dislocation of HMG(350)-HA and Insig-1-Myc requires metabolic energy and involves the AAA-ATPase p97/VCP. Sterols stimulate HMG(350)-HA and HMGR release to the cytosol concurrent with removal of their N-glycan by cytosolic peptide:N-glycanase. Sterols neither accelerate dislocation nor stimulate deglycosylation of ubiquitination-defective HMG(350)-HA((K89 + 248R)) mutant. Dislocation of HMG(350)-HA depends on Insig-1-Myc, whose dislocation and degradation are sterol independent. Coimmunoprecipitation experiments demonstrate sterol-stimulated association between HMG(350)-HA and Insig-1-Myc. Sterols do not enhance binding to Insig-1-Myc of HMG(350)-HA mutated in its sterol-sensing domain or of HMG(350)-HA((K89 + 248R)). Wild-type HMG(350)-HA and Insig-1-Myc coimmunoprecipitate from the soluble fraction only when both proteins were coexpressed in the same cell, indicating their encounter before or during dislocation, raising the possibility that they are dislocated as a tightly bound complex.
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PMID:Dislocation of HMG-CoA reductase and Insig-1, two polytopic endoplasmic reticulum proteins, en route to proteasomal degradation. 1945 99