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S Kornfeld

Publications and source records attributed to S Kornfeld.

At least 19 recordsLinked to original sources
PubMed1992

Lysosomal enzyme phosphorylation. I. Protein recognition determinants in both lobes of procathepsin D mediate its interaction with UDP-GlcNAc:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase.

We have investigated the nature of a protein domain that is shared among lysosomal hydrolases and is recognized by UDP-GlcNAc:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase, the initial enzyme in the biosynthesis of mannose 6-phosphate residues. Previously, elements of this recognition domain were identified using a chimeric protein approach. The combined substitution of two regions (amino acids 188-230, particularly lysine 203, and 265-292) from the carboxyl lobe of the lysosomal hydrolase cathepsin D into the homologous positions of the related secretory protein glycopepsinogen was sufficient to confer recognition by phosphotransferase and subsequent phosphorylation of the oligosaccharides when this chimeric protein was expressed in Xenopus oocytes. (Baranski, T. J., Faust, P. L., and Kornfeld, S. (1990) Cell 63, 281-291). The current study demonstrates that when these two regions are replaced in cathepsin D by the homologous glycopepsinogen amino acids, the resultant chimeric molecule is poorly phosphorylated. However, when either of these regions is substituted individually, the chimeric molecules are well phosphorylated. The phosphorylation of these latter chimeric proteins is dependent on the presence of procathepsin D amino lobe elements. By analyzing a series of chimeric proteins that contain all eight combinations of three consecutive segments of the entire amino lobe of procathepsin D, it was found that multiple regions of the amino lobe of cathepsin D enhance phosphorylation of the chimeric proteins. These elements may be part of an extended carboxyl lobe recognition domain or comprise a second independent recognition domain.

Amino Acid Sequence↗
PubMed1992

Lysosomal enzyme phosphorylation. II. Protein recognition determinants in either lobe of procathepsin D are sufficient for phosphorylation of both the amino and carboxyl lobe oligosaccharides.

Cathepsin D is a bilobed lysosomal aspartyl protease that contains one Asn-linked oligosaccharide/lobe. Each lobe also contains protein determinants that serve as recognition domains for binding of UDP-GlcNAc:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase, the first enzyme in the biosynthesis of the mannose 6-phosphate residues on lysosomal enzymes. In this study we examined whether the location of the protein recognition domain influences the relative phosphorylation of the amino and carboxyl lobe oligosaccharides. To do this, chimeric proteins containing either amino or carboxyl lobe sequences of cathepsin D substituted into a glycosylated form of the homologous secretory protein pepsinogen were expressed in Xenopus oocytes. The amino and carboxyl lobe oligosaccharides were then isolated from the various chimeric proteins and independently analyzed for their mannose 6-phosphate content. This analysis has shown that a phosphotransferase recognition domain located on either lobe of a cathepsin D/glycopepsinogen chimeric molecule is sufficient to allow phosphorylation of oligosaccharides on both lobes. However, phosphorylation of the oligosaccharide on the lobe containing the recognition domain is favored. We also found that the majority of the carboxyl lobe oligosaccharides of cathepsin D acquire two phosphates, whereas the amino lobe oligosaccharides only acquire one phosphate.

Animals↗
PubMed1992

Phosphorylation of Asn-linked oligosaccharides located at novel sites on the lysosomal enzyme cathepsin D.

We have examined the phosphorylation of Asn-linked oligosaccharides introduced at seven novel sites on human cathepsin D to determine whether the location of an oligosaccharide on a lysosomal enzyme affects its ability to serve as a substrate for UDP-GlcNAc:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase (phosphotransferase), the enzyme that catalyzes the initial step in the biosynthesis of mannose 6-phosphate residues. The glycosylation sites were introduced into the cathepsin D cDNA by site-directed mutagenesis and were selected to be widely distributed over the surface of the molecule. When the constructs were expressed in Xenopus oocytes, the oligosaccharides at each glycosylation site were phosphorylated at levels considerably above background (19-70% phosphorylation versus < 0.4% for the secretory protein glycopepsinogen). However, oligosaccharides located closer to the essential components of the phosphotransferase recognition domain (lysine 203 and amino acids 265-292) were phosphorylated better than oligosaccharides located further away. Similar results were obtained for oligosaccharides at homologous sites on a pepsinogen/cathepsin D chimera containing only lysine 203 and residues 265-319 of cathepsin D, although the absolute levels of phosphorylation were lower. These results demonstrate that there is considerable flexibility in the placement of glycosylation sites on cathepsin D in terms of the ability of the oligosaccharides to serve as substrates for phosphotransferase, although oligosaccharides located closer to the phosphotransferase recognition determinant are preferentially phosphorylated.

Animals↗
PubMed1992

A His-Leu-Leu sequence near the carboxyl terminus of the cytoplasmic domain of the cation-dependent mannose 6-phosphate receptor is necessary for the lysosomal enzyme sorting function.

The determinants on the cytoplasmic tail of the cation-dependent mannose 6-phosphate receptor (CD-MPR) required for lysosomal enzyme sorting have been analyzed. Mouse L cells deficient in the mannose 6-phosphate/insulin-like growth factor-II receptor were transfected with normal bovine CD-MPR cDNA or cDNAs containing mutations in the 67-amino acid cytoplasmic tail and assayed for their ability to target the lysosomal enzyme cathepsin D to lysosomes. Cells expressing the wild-type bovine CD-MPR sorted 67 +/- 2% of newly synthesized cathepsin D compared with the base-line value of 47 +/- 1%. The presence of mannose 6-phosphate in the medium did not affect the efficiency of cathepsin D sorting, indicating that the routing of the ligand-receptor complex is completely intracellular. Mutant receptors with the carboxyl-terminal His-Leu-Leu-Pro-Met67 residues deleted or replaced with alanines sorted cathepsin D below the base-line value. A mutant receptor with the outermost Pro-Met residues replaced with alanines sorted cathepsin D better than the wild-type receptor, indicating that the essential residues for sorting are the His-Leu-Leu sequence. Disruption of a putative casein kinase II phosphorylation site at Ser57 had no detectable effect on sorting. The mutant receptor with the five-amino acid deletion was able to bind to a phosphopentamannose affinity column, proving that its ligand binding site was grossly intact. Resialylation experiments showed that this mutant receptor recycled from the cell surface to the Golgi at a rate similar to the normal CD-MPR, indicating that the defect in sorting is at the level of the Golgi.

Amino Acid Sequence↗
PubMed1992

Characterization of the signal for rapid internalization of the bovine mannose 6-phosphate/insulin-like growth factor-II receptor.

The signal for rapid internalization of the mannose 6-phosphate/insulin-like growth factor II receptor has been localized to the sequence Tyr-Lys-Tyr-Ser-Lys-Val in positions 24-29 of its 163-residue cytoplasmic tail. Most of the activity of this signal is mediated by the carboxyl 4 amino acids, especially Tyr26 and Val29 (Canfield, W. M., Johnson, K. F., Ye, R. D., Gregory, W. and Kornfeld, S. (1991) J. Biol. Chem. 266, 5682-5688). In this study, we have tested the effect of a series of mutations on the internalization rate of a mutant receptor that contains a 29-amino acid cytoplasmic tail terminating with the 4-amino acid internalization sequence Tyr-Ser-Lys-Val. Replacement of Tyr26 with Phe or Trp gave rise to mutant receptors that were internalized at 10% the wild-type rate, while receptors with Ala, Leu, Ile, Val, or Asn at this position were totally inactive. Val29 could be replaced by other large hydrophobic residues (Phe, Leu, Ile, or Met) with no loss of activity, but the presence of Ala, Gly, Arg, Gln, or Tyr in this position inactivated the signal. Ser27 could be effectively replaced by many different amino acids, but not by Pro or Gly. However, Gly27 could be tolerated if the residues at positions 28 and 29 were also changed. A change in the 2-residue spacing between Tyr26 and Val29 destroyed the signal. These data show that the essential elements of this signal are an aromatic residue, especially a Tyr in the first position, separated from a large hydrophobic residue in the last position by 2 amino acids. The residues in positions 2 and 3 of the signal may have a modulating effect on its activity. The Tyr-Ser-Lys-Val signal could be moved to a more proximal region of the cytoplasmic tail with only a modest loss of activity. In addition, the signal could be effectively replaced by the putative 4-residue signals of seven other receptors and membrane proteins known to undergo rapid endocytosis, including the Tyr-Thr-Arg-Phe sequence of the transferrin receptor, a Type II membrane protein. These results are compatible with the 4-residue signals of this type being interchangeable, even among Type I and Type II membrane proteins.

Amino Acid Sequence↗
PubMed1992

Purification of UDP-N-acetylglucosamine:glycoprotein N-acetylglucosamine-1-phosphotransferase from Acanthamoeba castellanii and identification of a subunit of the enzyme.

UDP-N-acetylglucosamine:glycoprotein N-acetylglucosamine-1-phosphotransferase (GlcNAc-phosphotransferase) from the soil amoeba Acanthamoeba castellanii has been purified over 100,000-fold by means of wheat germ agglutinin-Sepharose affinity chromatography, DEAE-cellulose chromatography, concanavalin A-Sepharose affinity chromatography, orange A-agarose dye chromatography, and gel filtration on Superose 6. The most purified enzyme has an estimated specific activity of at least 5 mumol of GlcNAc-phosphate transferred/min/mg of protein using alpha-methylmannoside as acceptor. The molecular weight of the native enzyme is approximately 250,000, as determined by gel filtration and glycerol gradients in H2O and D2O. A protein with an apparent M(r) of 97,000 in small scale preparations and its putative proteolytic fragment of 43,000 in large scale preparations co-purifies with the enzyme activity. This protein is covalently modified with GlcNAc-[32P]phosphate when the enzyme preparation is incubated with [beta-32P]UDP-GlcNAc in the absence of an acceptor substrate. The labeling of the 97(43)-kDa protein requires active enzyme and is completely inhibited by the addition of the acceptor substrate alpha-methylmannoside. The GlcNAc-[32P]phosphate transferred to the protein is not bound to serine, threonine, tyrosine, or mannose residues. The 97(43)-kDa protein with covalently bound GlcNAc-P does not serve as a kinetically competent enzyme-substrate intermediate. However, preincubation of GlcNAc-phosphotransferase with UDP-GlcNAc does result in a decrease in the Vmax of the enzyme in subsequent assays. Taken together, these data are consistent with the 97(43)-kDa protein being a subunit of GlcNAc-phosphotransferase.

Acanthamoeba↗
PubMed1992

Characterization of UDP-N-acetylglucosamine:glycoprotein N-acetylglucosamine-1-phosphotransferase from Acanthamoeba castellanii.

The kinetic properties of UDP-N-acetylglucosamine:glycoprotein N-acetylglucosamine-1-phosphotransferase (GlcNAc-phosphotransferase) partially purified from the soil amoeba Acanthamoeba castellanii have been studied. The transferase phosphorylated the lysosomal enzymes uteroferrin and cathepsin D 3-90-fold better than nonlysosomal glycoproteins and 16-83-fold better than a Man9GlcNAc oligosaccharide. Deglycosylated uteroferrin was a potent competitive inhibitor of the phosphorylation of intact uteroferrin (Ki of 48 microM) but did not inhibit the phosphorylation of RNase B or the simple sugar alpha-methylmannoside. Deglycosylated RNase (RNase A) did not inhibit the phosphorylation of RNase B or uteroferrin. These results indicate that purified amoeba GlcNAc-phosphotransferase recognizes a protein domain present on lysosomal enzymes but absent in most nonlysosomal glycoproteins. The transferase also exhibited a marked preference for oligosaccharides containing mannose alpha 1,2-mannose sequences, but this cannot account for the high affinity binding to lysosomal enzymes. A. castellanii extracts do not contain detectable levels of N-acetylglucosamine-1-phosphodiester alpha-N-acetylglucosaminidase, the second enzyme in the biosynthetic pathway for the mannose 6-phosphate recognition marker. We conclude that A. castellanii does not utilize the phosphomannosyl sorting pathway despite expression of very high levels of GlcNAc-phosphotransferase.

Acanthamoeba↗
PubMed1992

A method for [3H]mannose labeling of Asn-linked oligosaccharides on recombinant glycoproteins synthesized in Xenopus oocytes.

We have developed an efficient method for labeling the Asn-linked oligosaccharides of recombinant glycoproteins synthesized in Xenopus laevis oocytes. By coinjecting GDP-[3,4-(3)H]mannose with mRNA for human cathepsin D, it was possible to incorporate as much as 1800 cpm per oocyte into each of the two Asn-linked oligosaccharides of this glycoprotein. Overall, about 50% of the microinjected GDP-[3,4-(3)H]mannose was incorporated into Asn-linked oligosaccharides, a 10-fold greater value than that obtained when [2-(3)H]mannose was microinjected. Less than 10% of the injected GDP-[3,4-(3)H]mannose was metabolized to water or converted to amino acids. This technique should facilitate studies of Asn-linked oligosaccharide biosynthesis, processing, and structure in recombinant proteins synthesized in Xenopus oocytes.

Animals↗
PubMed1992

The cytoplasmic tail of the mannose 6-phosphate/insulin-like growth factor-II receptor has two signals for lysosomal enzyme sorting in the Golgi.

The mannose 6-phosphate/insulin-like growth factor-II (Man-6-P/IGF-II) receptor is known to cycle between the Golgi, endosomes, and the plasma membrane. In the Golgi the receptor binds newly synthesized lysosomal enzymes and transports them directly to an endosomal (prelysosomal) compartment without traversing the plasma membrane. Deletion of the carboxyl-terminal Leu-Leu-His-Val residues of the 163 amino acid cytoplasmic tail of the bovine Man-6-P/IGF-II receptor partially impaired this function, resulting in the diversion of a portion of the receptor-ligand complexes to the cell surface, where they were endocytosed. The same phenotype was observed when 134 residues of the cytoplasmic tail were deleted from the carboxyl terminus. Disruption of the Tyr24-Lys-Tyr-Ser-Lys-Val29 plasma membrane internalization signal alone had little effect on Golgi sorting, but when combined with either deletion resulted in a complete loss of this function. The mutant receptors retained the ability to recycle to the Golgi and bind cathepsin D. These results indicate that the cytoplasmic tail of the Man-6-P/IGF-II receptor contains two signals that contribute to Golgi sorting, presumably by interacting with the Golgi clathrin-coated pit adaptor proteins. The Leu-Leu-containing sequence represents a novel motif for mediating interaction with Golgi adaptor proteins.

Amino Acid Sequence↗
PubMed1991

The bovine mannose 6-phosphate/insulin-like growth factor II receptor. Localization of mannose 6-phosphate binding sites to domains 1-3 and 7-11 of the extracytoplasmic region.

The extracytoplasmic region of the 270-kDa mannose 6-phosphate/IGF-II receptor is composed of 15 repeating domains and is capable of binding 2 mol of mannose 6-phosphate (Man-6-P). To localize the Man-6-P binding domains, bovine receptor was subjected to partial proteolysis with subtilisin followed by affinity chromatography on pentamannosyl phosphate-agarose. Eleven proteolytic fragments ranging in apparent molecular mass from 53 to 206 kDa were isolated. Sequence analysis of six of the fragments localized their amino termini to either the beginning of domain 1 at the amino terminus of the molecule or the beginning of domain 7, according to the alignment of Lobel et al. (Lobel, P., Dahms, N. M., and Kornfeld, S. (1988) J. Biol. Chem. 263, 2563-2570). The smallest fragment, with an apparent molecular mass of 53 kDa, is predicted to encompass domains 1-3. Another fragment, with an apparent molecular mass of 82 kDa, is predicted to encompass domains 7-10 or 7-11. The Man-6-P binding site contained within domains 1-3 was further defined by expressing truncated forms of the receptor in Xenopus laevis oocytes and assaying their ability to bind phosphomannosyl residues. A soluble polypeptide containing domains 1-3 exhibited binding activity, whereas a polypeptide containing domains 1 and 2 did not. This indicates that domain 3 is a necessary component of one of the Man-6-P binding sites of the receptor.

Amino Acid Sequence↗
PubMed1991

Mapping and molecular modeling of a recognition domain for lysosomal enzyme targeting.

Lysosomal enzymes contain a common protein determinant that is recognized by UDP-GlcNAc:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase, the initial enzyme in the biosynthesis of mannose-6-P residues. Previously, we generated a lysosomal enzyme recognition domain by substituting two regions (lysine 203 and amino acids 265-292) of the lysosomal hydrolase cathepsin D into a related secretory protein glycopepsinogen. When expressed in Xenopus oocytes, the oligosaccharides of the chimeric protein were efficiently phosphorylated (Baranski, T. J., Faust, P. L., and Kornfeld, S. (1990) Cell 63, 281-291). In the current study, incremental substitutions of cathepsin D residues into glycopepsinogen and alanine-scanning mutagenesis were utilized to define the recognition domain more precisely. A computer-generated model of the cathepsin D/pepsinogen chimeric molecule served as a guide for mutagenesis and for the interpretation of results. These studies indicate that the recognition domain is a surface patch that contains multiple interacting sites. There is a strict positional requirement for the lysine residue at position 203.

Amino Acid Sequence↗
PubMed1991

Phase I trial of H65-RTA immunoconjugate in patients with cutaneous T-cell lymphoma.

H65-RTA is an immunoconjugate that consists of the A chain of ricin (RTA), a ribosomal-inhibiting protein, coupled to a murine monoclonal antibody (H65) directed against the pan-T-cell antigen CD5. The CD5 antigen is heterogeneously expressed on cutaneous T-cell lymphoma tumor cells, but is not expressed on normal cells except lymphocytes. A phase I trial was therefore conducted in which 14 patients with cutaneous T-cell lymphoma progressive on other therapies were treated with up to three cycles of H65-RTA. The maximal tolerated dose (MTD) of H65-RTA was 0.33 mg/kg/d administered intravenously for 10 days as defined by dyspnea at rest at higher doses. Other reversible side effects included myalgia, mild hypoalbuminemia with weight gain, pedal edema, fatigue, fevers, and chills. Six patients received more than one cycle of H65-RTA without increased side effects compared with the first cycle. Pharmacokinetic analysis showed that peak serum drug levels were dose-dependent, and ranged from 1.13 to 5.56 micrograms/mL, with a terminal half-life ranging from 1.0 to 2.9 hours. The development of antibodies against the immunoconjugate was associated with a lower peak drug level, but not with enhanced side effects. Partial responses lasting from 3 to 8 months were documented in four patients. Three of the responding patients received more than one cycle of H65-RTA in the presence of anti-immunoconjugate antibodies. The results from this phase I trial suggest that H65-RTA is an active drug in the treatment of cutaneous T-cell lymphoma. The immunoconjugate may be safely administered repeatedly, even in the presence of anti-immunoconjugate antibodies, with responses noted. Additional studies at the MTD are needed to define the response rate in this disease.

Adult↗
PubMed1991

Localization of the signal for rapid internalization of the bovine cation-independent mannose 6-phosphate/insulin-like growth factor-II receptor to amino acids 24-29 of the cytoplasmic tail.

The signal for the rapid internalization of the cation-independent mannose 6-phosphate/insulin-like growth factor-II receptor has been previously localized to the inner half of the 163-amino acid cytoplasmic tail, including tyrosine 24 and tyrosine 26 (Lobel, P., Fujimoto, K., Ye, R. D., Griffiths, G., and Kornfeld, S. (1989) Cell 57, 787-796). To define this signal more precisely, we generated a series of truncation and substitution mutants and analyzed them for their ability to mediate the endocytosis of extracellular lysosomal enzymes. Mutant receptors containing cytoplasmic domains of 29 or more amino acids functioned normally in endocytosis whereas a mutant receptor with a 28-amino acid cytoplasmic domain was internalized extremely slowly. Alanine scanning of the region between amino acids 19 and 30 identified tyrosine 26 and valine 29 as the most important residues for rapid receptor internalization. Tyrosine 24 and lysine 28 also contributed to the signal while the other amino acids were not critical. The tyrosine residues could be substituted with phenylalanines with no loss of activity, indicating the requirement for an aromatic residue in these positions rather than tyrosine specifically. Conservative substitutions of arginine or histidine for lysine 28 also preserved the internalization signal. These results indicate that the sequence Tyr-Lys-Tyr-Ser-Lys-Val serves as the internalization signal for the mannose 6-phosphate/insulin-like growth factor-II receptor. The crucial elements of this sequence are present in the cytoplasmic tails of a number of other membrane receptors and proteins known to undergo rapid internalization.

Amino Acid Sequence↗
PubMed1990

Generation of a lysosomal enzyme targeting signal in the secretory protein pepsinogen.

Lysosomal enzymes contain a common protein determinant that is recognized by UDP-GlcNAc:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase, the initial enzyme in the formation of mannose 6-phosphate residues. To identify this protein determinant, we constructed chimeric molecules between two aspartyl proteases: cathepsin D, a lysosomal enzyme, and pepsinogen, a secretory protein. When expressed in Xenopus oocytes, the oligosaccharides of cathepsin D were efficiently phosphorylated, whereas the oligosaccharides of a glycosylated form of pepsinogen were not phosphorylated. The combined substitution of two noncontinuous sequences of cathepsin D (lysine 203 and amino acids 265-292) into the analogous positions of glycopepsinogen resulted in phosphorylation of the oligosaccharides of the expressed chimeric molecule. These two sequences are in direct apposition on the surface of the molecule, indicating that amino acids from different regions come together in three-dimensional space to form this recognition domain. Other regions of cathepsin D were identified that may be components of a more extensive recognition marker.

Amino Acid Sequence↗
PubMed1990

Cation-dependent mannose 6-phosphate receptor contains two internalization signals in its cytoplasmic domain.

The signals required for rapid internalization of the bovine cation-dependent mannose 6-phosphate receptor have been localized to two distinct regions of the 67-amino acid cytoplasmic domain. One signal includes phenylalanine 13 and phenylalanine 18, while the other involves tyrosine 45. The former signal is more potent than the latter, but both must be present for the maximal rate of receptor internalization. Each signal shares similarities with the known internalization signals of other recycling receptors.

Amino Acid Sequence↗