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W J Welch

Publications and source records attributed to W J Welch.

At least 109 records · Page 6Linked to original sources
PubMed1991

The role of heat-shock proteins as molecular chaperones.

Recent studies have revealed that protein folding and assembly events in vivo require the participation of accessory components, now being referred to as 'molecular chaperones'. A number of chaperones have been identified as members of the heat-shock (or stress) protein family. This review discusses the roles of two classes of chaperones, the heat-shock protein 70 and groEL/ES families, in facilitating protein maturation, and describes how such events are perturbed in the cell subjected to metabolic stress.

Bacterial Proteins↗
PubMed1991

Thromboxane mediates renal hemodynamic response to infused angiotensin II.

UNLABELLED: Since we had found that angiotensin II (Ang II), but not phenylephrine (PE), increased the excretion of thromboxane (Tx) and raised mean arterial pressure (MAP) by a Tx-dependent mechanism, we tested the role of TxA2 in mediating Ang II-induced changes in renal hemodynamics. For series 1, groups of anesthetized rats received an i.v. infusion of Ang II (50 ng.kg-1.min-1). When infused with a vehicle, Ang II increased MAP, renal vascular resistance (RVR) and the excretion of TxB2 factored by GFR. A PGH2-TxA2 receptor antagonist, SQ-29,548, or three days of pretreatment with a TxA2 synthase inhibitor UK-38,485, which reduced excretion of TxB2 by 80%, blunted the rise in MAP and RVR induced by Ang II. In contrast, three days of pretreatment with indomethacin did not alter the renal vascular response to Ang II. For series 2, groups of rats received Ang II at a higher rate (500 ng.kg-1.min-1) while the RPP was stabilized at +11 to +15 mm Hg with a suprarenal aortic clamp. SQ-29,548 and UK-38,485 both prevented Ang II-induced reductions in GFR and blocked 80% of the increase in RVR. For series 3, infusions of phenylephrine at an equipressor dose to series 2 of 30 micrograms.kg-1.min-1 with control of RPP at +14 mm Hg also increased RVR but this was not blunted by SQ-29,548. IN CONCLUSION: 1.) infusion of Ang II increases excretion of filtered TxB2, causes dose-dependent increases in RVR and, at high doses, reduces GFR.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1991

The two mammalian mitochondrial stress proteins, grp 75 and hsp 58, transiently interact with newly synthesized mitochondrial proteins.

In mammalian cells, two of the so-called heat shock (hsp) or stress proteins are components of the mitochondria. One of these, hsp 58, is a member of the bacterial GroEL family, whereas the other, glucose-regulated protein (grp) 75, represents a member of the hsp 70 family of stress proteins. Owing to previous studies implicating a role for both the hsp 70 and GroEL families in facilitating protein maturation events, we used the method of native immunoprecipitation to examine whether hsp 58 and grp 75 might interact with other proteins of the mitochondria. In cells pulse-labeled with [35S]-methionine, a significant number of newly synthesized mitochondrial proteins co-precipitated with either hsp 58 or grp 75. Such interactions appeared transient. For example, providing the pulse-labeled cells a subsequent chase period in the absence of radiolabel resulted in a reduction of co-precipitating proteins. If the pulse-chase labeling experiments were performed in the presence of an amino acid analogue, somewhat different results were obtained. Specifically, although many of the newly synthesized and analogue-containing proteins again were observed to co-precipitate with grp 75, the interactions did not appear transient, but instead were stable. Under steady-state labeling conditions, we also observed a portion of hsp 58 and grp 75 in an apparent complex with one another. On addition of ATP, the complex was dissociated. Accompanying this dissociation was the concomitant autophosphorylation of grp 75. On the basis of these observations, as well as previous studies examining the structure/function of the hsp 70 and GroEL proteins, we suspect that both hsp 58 and grp 75 interact with and facilitate the folding and assembly of proteins as they enter into the mitochondria.

Adenosine Triphosphate↗
PubMed1991

The response of guinea pig airway epithelial cells and alveolar macrophages to environmental stress.

Cells lining the respiratory tract form an interface between the organism and the external environment and are repeatedly exposed to physical, chemical, and metabolic stresses. We examined the response of cultured guinea pig tracheal epithelial cells and alveolar macrophages to various forms of stress, including clinically and environmentally relevant metabolic stresses such as ozone and acid exposure. Classic stress treatments such as heat shock and sodium arsenite treatment induced the synthesis of 28, 32, 72, 73, 90, and 110 kD stress proteins similar to those observed in other cell types. In contrast, no significant changes in the pattern of protein synthesis were detected after exposure to ambient concentrations of ozone, although ozone exposure caused significant cytotoxicity to both cell types. Another potent oxidant, hydrogen peroxide, similarly did not induce appreciable stress protein synthesis. However, surface acidification of tracheal epithelial cells and alveolar macrophages caused the induction of 72 and 78 kD stress proteins. While stress proteins may play a role in the response of respiratory cells to certain injuries such as hyperthermia and surface acidification, they may not be important in the defense against ozone or other forms of oxidative injury.

Animals↗
PubMed1991

Evidence that heat shock protein-70 associated with progesterone receptors is not involved in receptor-DNA binding.

In the absence of hormone, human progesterone receptors (PR) are recovered in the cytosolic fraction of cell lysates as a multimeric complex containing the steroid-binding polypeptide, heat shock protein-90 (hsp90), and heat shock protein-70 (hsp70). Activated forms of human PR that acquire the ability to bind to DNA are dissociated from hsp90, but retain association with hsp70. The present study has examined whether associated hsp70 has a function in receptor-DNA binding. When activated PR was bound to specific target DNA in a gel shift assay, no hsp70 was detectable in the PR-DNA complex, as evidenced by the failure of several antibodies to hsp70 to affect the mobility or the amount of complexes. To determine whether hsp70 might indirectly influence DNA-binding activity, we have examined the effect of hsp70 dissociation on PR-DNA-binding activity. Dissociation was achieved either by treatment of immunoaffinity-purified immobilized PR complexes with ATP or by the binding of PR complexes to ATP-agarose, followed by elution with high salt. Under both conditions, dissociation from hsp70 neither enhanced nor impaired the ability of PR to bind to specific DNA. These results suggest that hsp70 is not involved in PR binding to DNA, either directly by participating in DNA binding or indirectly by modulating PR-DNA-binding activity. This implies that hsp70 functions at an earlier stage in the receptor activation pathway. Consistent with the known involvement of hsp70 in stabilizing unfolded states of other target proteins, we propose that hsp70 may assist in nuclear transport of PR or in assembly-disassembly of the 8-10S multimeric complex.

Blotting, Western↗
PubMed1991

Expression of heat shock proteins in Alzheimer's disease.

In an investigation of heat shock proteins (HSPs) in the brains of Alzheimer's disease (AD) patients and cognitively intact control subjects, we found that 2 HSPs, termed "HSP72" and "GRP78," underwent major changes in expression in AD. HSP72, which was present at very low levels in control brains, increased dramatically in AD patients, and was localized exclusively in neuritic plaques and neurofibrillary tangles. We hypothesize that HSP72 is induced as an early response to the formation of abnormal proteins, perhaps targeting them for proteolysis. In contrast, GRP78 increased in AD only in neurons that remained cytologically normal, especially in the CA3 subfield of the hippocampus and the deep layers of the entorhinal cortex. The increased expression of GRP78 within successfully surviving neurons suggests that this protein may protect such cells from AD-specific damage.

Aged↗
PubMed1991

Mechanism of renal vasoconstriction with thromboxane mimetic: engagement of tubuloglomerular feedback.

U-46,619 infused at 10 ng.kg-1.min-1 in anesthetized rats reduced the glomerular capillary pressure only during engagement of tubuloglomerular feedback (TGF). 100 ng.kg-1.min-1 induced renal vasoconstriction, whereas femoral vasoconstriction and a rise in BP required 1,000-10,000 ng.kg-1.min-1. These results implicate TGF in the extreme sensitivity of the kidney to TxA2/PG endoperoxide receptor activation.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1990

Constitutive expression of a groEL-related protein on the surface of human gamma/delta cells.

Rabbit antibodies to hsp58 (P1), the human homologue of the Escherichia coli stress protein groEL, react specifically in indirect immunofluorescence and complement-dependent microcytoxicity experiments with a cell surface antigen expressed constitutively by T cell lines bearing gamma/delta receptors. This anti-hsp58-reactive antigen is not demonstrable on T cells that express alpha/beta receptors or on various cells that lack T cell receptors. Certain evidence was obtained to suggest that the target antigen on the surface of gamma/delta T cells is a approximately 77-kD protein distinct from intracellular hsp58 and known members of the hsp70 stress protein family. While the exact nature and significance of this anti-hsp58-reactive protein remain to be determined, these data may help to clarify the roles of groEL-related stress proteins and gamma/delta cells that recognize groEL homologous in immunologic defense against infection and in autoimmune disease.

Antibodies↗
PubMed1990

Recognition by human V gamma 9/V delta 2 T cells of a GroEL homolog on Daudi Burkitt's lymphoma cells.

All human gamma delta T cells coexpressing the products of the variable (V) region T cell receptor (TCR) gene segments V gamma 9 and V delta 2 recognize antigens from mycobacterial extracts and Daudi cells. Exogenous and endogenous ligands on the cell surface, homologous to the groEL heat shock family, induced reactivities that resembled superantigen responses in this major subset of human peripheral blood gamma delta T cells. Stimulation of human V gamma 9/V delta 2 T cells is not restricted by human leukocyte antigens (HLA), including nonpolymorphic beta 2-microglobulin (beta 2M)-associated class Ib molecules. These data may be important for understanding the role of gamma delta T cells in autoimmunity and in responses to microorganisms and tumors.

Antigen-Presenting Cells↗
PubMed1990

Interaction of Hsp 70 with newly synthesized proteins: implications for protein folding and assembly.

The 70-kilodalton family of heat shock proteins (Hsp 70) has been implicated in posttranslational protein assembly and translocation. Binding of cytosolic forms of Hsp 70 (Hsp 72,73) with nascent proteins in the normal cell was investigated and found to be transient and adenosine triphosphate (ATP)-dependent. Interaction of Hsp 72,73 with newly synthesized proteins appeared to occur cotranslationally, because nascent polypeptides released prematurely from polysomes in vivo can be isolated in a complex with Hsp 72,73. Moreover, isolation of polysomes from short-term [35S]Met-labeled cells (pulsed) revealed that Hsp 72,73 associated with nascent polypeptide chains. In cells experiencing stress, newly synthesized proteins coimmunoprecipitated with Hsp 72,73; however, in contrast to normal cells, interaction with Hsp 72,73 was not transient. A model consistent with these data suggests that under normal growth conditions, cytosolic Hsp 72,73 interact transiently with nascent polypeptides to facilitate proper folding, and that metabolic stress interferes with these events.

Adenosine Triphosphate↗
PubMed1990

Identification of p70 and p80 associations with class II MHC molecules and Ii.

Two proteins, p70 and p80, were found in chemically crosslinked complexes with class II MHC molecules and Ii after 3-12 hr labelings with [35S]methionine. Two-dimensional, nonreduced/reduced SDS gel electrophoresis of immunoprecipitated complexes revealed 1) endogenous disulfide linkages between Ii-Ii and Ii-p70 and 2) chemically crosslinked, nearest neighbors of alpha-beta, alpha-Ii, Ii-p70, and alpha-p80. Although such nearest neighbors within multimeric complexes were identified as dimers in nonreduced/reduced 2D gels, stoichiometries could not be determined in the high molecular weight complex(es), which included alpha, beta, Ii, p70, and p80, and were not separated in the first dimension. p80 was not the chondroitin-sulfate form of Ii (Ii-CS) because it was not electrophoretically heterogeneous and was not sensitive to chondroitinase ABC. p70 was not hsp72/74 detected with C92 or N27 mAbs, and p80 was not BiP detected with its respective mAb. While only these two proteins associated prominently with class II MHC antigens and Ii late after synthesis, their functions are unknown.

Antibodies, Monoclonal↗
PubMed1990

Cumulative effects of cycle length on ventricular refractoriness in man.

This study examined the time course of changes of ventricular effective refractory period (VERP) following an abrupt change of cycle length (CL) in man. Stimulation at the right ventricular apex consisted of 19 cycles of an initial CL, followed by a variable number of cycles (0 to 50 cycles) of a new CL, and an extrastimulus to test for VERP. Fifteen patients were enrolled in each part of the study. In part A, initial CLs were long (mean +/- standard error, 650 +/- 20 msec) and new CLs were short (325 +/- 10 msec). VERPs were 259 +/- 6 msec after the long cycles, 238 +/- 6 msec after one short cycle (p less than 0.05), 224 +/- 5 msec after 10 short cycles, and 210 +/- 6 msec after 50 short cycles (p less than 0.05 versus 1 or 10 short cycles). Thus 43% of total shortening of VERP occurred in the first short cycle and 57% occurred in subsequent short cycles. In part B, initial CLs were short and new CLs were long. VERPs were 212 +/- 7 msec after the short cycles, 237 +/- 7 msec after one long cycle (p less than 0.05), 239 +/- 7 msec after 10 long cycles, and 247 +/- 7 msec after 50 long cycles (p less than 0.05 versus 1 or 10 long cycles). Thus 71% of total lengthening of VERP occurred in the first long cycle and 29% occurred in subsequent long cycles. In conclusion, following an abrupt change of CL in man, VERP changes markedly in the first new cycle (immediate effect) and then undergoes further, more gradual change over a large number of subsequent cycles (cumulative effects). Cumulative effects appear to be greater following shortening of CL than following lengthening of CL.

Adult↗
PubMed1990

Characterization and inducibility of hsp 70 proteins in the male mouse germ line.

The properties and inducibility of the heat shock protein 70 (hsp 70) gene products were examined during differentiation of mouse testicular cells by one and two-dimensional gel electrophoresis and immunoblotting. Low levels of the 72- and 73-kD heat shock proteins normally found in mouse cell lines were detected in the mouse testis. A novel isoform with a relative molecular mass of 73 kD (called 73T) was also observed, in the presence or absence of heat shock. 73T was shown to be produced by germ cells since it was not detected in testes from mutant mice devoid of germ cells. Furthermore, 73T was found only in adult mouse testicular cells, not in testes from animals that lack meiotic germ cells. 73T was synthesized in enriched cell populations of both meiotic prophase and postmeiotic cells, but was not inducible by in vitro heat shock. In the adult testis, low levels of the bona fide 72-kD heat-inducible (hsp72) were induced in response to elevated temperatures. In contrast, in testes from animals in which only somatic cells and premeiotic germ cells were present, there was a substantial induction of hsp 72. It is suggested that hsp 72 is inducible in the somatic compartment and possibly in the premeiotic germ cells, but not in germ cells which have entered meiosis and which are expressing members of the hsp 70 gene family in a developmentally regulated fashion.

Animals↗
PubMed1990

Thromboxane mediation of the pressor response to infused angiotensin II.

UNLABELLED: The role of thromboxane A2(Tx) in mediating the pressor response to angiotensin II (AII) was studied in anesthetized rats. Intravenous AII (500 ng/kg/min) increased mean arterial pressure (MAP) by 35 +/- 3 mm Hg and increased the excretion of prostaglandin PGE2, the metabolites of prostacyclin (6kPGF1 alpha) and Tx (TxB2) (P less than .05). A similar pressor infusion of the alpha 1-adrenoreceptor agonist phenylephrine (PE) increased the excretion of PGE2 and 6kPGF1 alpha but not TxB2. The increases in MAP and prostaglandin excretion produced by AII were reversed by the AII-receptor antagonist saralasin (10 micrograms/kg/min) while those produced by PE were reversed by the alpha-adrenoreceptor antagonist phenoxybenzamine (250 micrograms/kg). The Tx receptor antagonist, SQ-29,548 (8 mg/kg) attenuated (P less than .0001) the AII-induced rise in MAP (13 +/- 1 mm Hg) but did not modify the pressor response to PE. The Tx synthetase inhibitor, UK-38,485 (50 mg/kg/d) given for 3 days, reduced basal TxB2 excretion by 75% and also attenuated (P less than .001) the AII-induced rise in MAP (11 +/- 2 mm Hg). However, when given 40 min before the AII infusion, UK-38,485 did not attenuate the pressor response. In separate groups of rats, the log dose-response curve for bolus intravenous injection of AII was shifted to the right by SQ-29,548 while that for PE was unaffected. IN CONCLUSION: 1) AII releases Tx; 2) Tx release is not secondary to hypertension; and 3) Tx can mediate up to two-thirds of the short-term pressor response to high-dose AII infusion.

Angiotensin II↗
PubMed1990

Feedback responses during sequential inhibition of angiotensin and thromboxane.

Since thromboxane (Tx) can mediate the actions of angiotensin II (ANG II), we investigated interaction between these systems on the tubuloglomerular feedback (TGF) response. TGF was assessed from proximal stop-flow pressure (PSF) during orthograde perfusion of the loop of Henle (LH) between 0 and 40 nl/min. In the basal state, TGF was 11.3 +/- 0.8 mmHg. In series 1 experiments, it was unaltered by vehicle (+0.3 +/- 0.9 mmHg, n = 9, NS), was reduced by an ANG II antagonist, saralasin (-2.4 +/- 1.1 mmHg, n = 8, P less than 0.0005), and by a TxA2 antagonist SQ 29,548 (-4.8 +/- 0.6 mmHg, n = 11, P less than 0.0001). Both drugs together produced an additive blunting of TGF of -6.9 +/- 0.7 mmHg. In series 2 experiments, TGF was again unchanged by vehicle (+0.2 +/- 0.6 mmHg). It was reduced by -4.4 +/- 0.2 mmHg (P less than 0.0001) by an angiotensin-converting enzyme inhibitor CGS-14,824A (50 mg/kg, n = 5) and by -4.0 +/- 0.4 mmHg (P less than 0.001) by a Tx synthesis inhibitor CGS-13,080 (50 mg/kg, n = 7). Although both drugs together produced a further blunting of the response of -6.1 +/- 0.4 mmHg, this was significantly (P less than 0.001) less than additive. In both series, a response (averaging 3.5 +/- 0.3 mmHg) persisted in all rats given combined antagonists or inhibitors. In conclusion, both ANG II and TxA2 can modulate TGF-induced changes in PSF independently, and the response probably requires other system(s) in addition to ANG II and TxA2.

Angiotensin II↗
PubMed1990

Heat shock proteins bind calcitonin.

We have demonstrated two heat shock proteins (HSP's) in the human placenta that specifically bind calcitonin. Binding specificity was shown by ligand-affinity chromatography and by competitive binding studies. The HSP's were identified by Western analysis and by amino acid sequence. Our observations are consistent with the hypothesis that HSP's may function by binding and interacting with cellular proteins and peptides during their biogenesis. This interaction may both depend upon and produce conformational changes in these ligands during their intracellular processing. Additionally, HSP-peptide hormone interactions may confound studies designed to investigate classical receptor-hormone interactions.

Amino Acid Sequence↗
PubMed1990

Angiotensin II and thromboxane in the regulation of blood pressure and renal function.

UNLABELLED: In experiments in anesthetized rats, the hypothesis that angiotensin II (Ang II) infusion released thromboxane (TxA2) which modulated the systemic and renal vasoconstriction was tested. Intravenous Ang II (500 ng.kg-1.min-1) increased MAP by 35 +/- 3 mm Hg and the excretion of TxB2 (P less than 0.03), whereas a similar pressor infusion of phenylephrine did not increase TxB2 excretion. A TxA2 receptor antagonist (TxRA) SQ-29,548 (8 mg.kg-1.hr-1) or pretreatment with a thromboxane synthesis inhibitor (TSI), UK-38,485 (50 mg.kg-1.day-1 x 3) blunted (P less than 0.005) the pressor response to 12 +/- 2 and 11 +/- 2 mm Hg, respectively, whereas TxRA did not modify the pressor response to phenylephrine. Infusion of Ang II at a dose of 50 ng.kg-1.min-1 reduced the GFR and increased the filtration fraction and renal vascular resistance. TxRA blunted (P less than 0.01) these effects of Ang II. IN CONCLUSION: 1.) Ang II releases TxA2 within the kidney independent of hypertension; 2.) TxA2 can mediate much of the pressor and renal hemodynamic responses to Ang II.

Angiotensin II↗