Biomedical subjects

D J Kwiatkowski

Publications and source records attributed to D J Kwiatkowski.

At least 55 records · Page 3Linked to original sources

PubMed1998

Tuberous sclerosis gene 2 product modulates transcription mediated by steroid hormone receptor family members.

Tuberous sclerosis (TSC) is a genetic disorder that results in the development of hamartomatous lesions in a variety of organ systems. Both the prevalence of the disease and the often devastating consequences of these tumors pose a serious health and medical care problem. The disease has been mapped to two distinct genetic loci in humans, and although the genes (TSC1 and TSC2) for both loci have recently been cloned, their function remains an enigma. Data presented here demonstrates that TSC2 protein can bind and selectively modulate transcription mediated by members of the steroid receptor superfamily of genes. These data place TSC2 into a growing list of nuclear receptor coregulators and strengthen the expanding body of evidence that these coregulators may play critical roles in cellular differentiation.

Amino Acid Sequence↗

PubMed1998

Gelsolin is a downstream effector of rac for fibroblast motility.

Rac, a member of the rho family of GTPases, when activated transmits signals leading to actin-based membrane ruffling in fibroblasts. Compared with wild-type fibroblasts, gelsolin null (Gsn-) dermal fibroblasts have a markedly reduced ruffling response to serum or EGF stimulation, which signal through rac. Bradykinin-induced filopodial formation, attributable to activation of cdc42, is similar in both cell types. Wild-type fibroblasts exhibit typical lamellipodial extension during translational locomotion, whereas Gsn- cells move 50% slower using structures resembling filopodia. Multiple Gsn- tissues as well as Gsn- fibroblasts overexpress rac, but not cdc42 or rho, 5-fold. Re-expression of gelsolin in Gsn- fibroblasts by stable transfection or adenovirus reverts the ruffling response, translational motility and rac expression to normal. Rac migrates to the cell membrane following EGF stimulation in both cell types. Gelsolin is an essential effector of rac-mediated actin dynamics, acting downstream of rac recruitment to the membrane.

Actins↗

PubMed1998

Caspase-3-induced gelsolin fragmentation contributes to actin cytoskeletal collapse, nucleolysis, and apoptosis of vascular smooth muscle cells exposed to proinflammatory cytokines.

Gelsolin, an 80 kDa actin-severing protein, has been recently identified as a substrate for the cell death-promoting cysteinyl protease caspase-3 (CPP32/apopain/YAMA). We investigated the role of gelsolin and its cleavage product in apoptosis of vascular smooth muscle cells (SMC) induced by the proinflammatory cytokines interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha). Treatment with a combination of IFN-gamma and TNF-alpha reduced viability of SMC in a time- and concentration-dependent manner. Immunoblotting revealed that SMC treated with the cytokines generated a 41 kDa gelsolin fragment. The gelsolin fragmentation required activation of caspase-3, as the caspase-3 inhibitor diminished cytokine-induced cell death as well as the fragmentation. Gelsolin cleavage was accompanied by a reduction in F-actin content and by a marked disruption of cell structure. Adenovirus-mediated transfection of this N-terminal gelsolin fragment into SMC altered cell morphology, reduced cell viability, increased the number of TUNEL-positive cells, and promoted internucleosomal DNA fragmentation. Compared to wild-type cells, gelsolin-deficient SMC showed resistance to apoptosis induced by the inflammatory cytokines. These results suggest a mechanistic role for gelsolin cleavage during SMC apoptosis, a process implicated in vessel development as well as stability of atherosclerotic plaque.

Actins↗

PubMed1998

Probing the phosphoinositide 4,5-bisphosphate binding site of human profilin I.

BACKGROUND: Profilin is a widely and highly expressed 14 kDa protein that binds actin monomers, poly(L-proline) and polyphosphoinositol lipids. It participates in regulating actin-filament dynamics that are essential for many types of cell motility. We sought to investigate the site of interaction of profilin with phosphoinositides. RESULTS: Human profilin I was covalently modified using three tritium-labeled 4-benzoyldihydrocinnamoyl (BZDC)-containing photoaffinity analogs of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2). The P-1-tethered D-myoinositol 1,4,5-trisphosphate (Ins(1,4,5)P3) modified profilin I efficiently and specifically; the covalent labeling could be displaced by co-incubation with an excess of PtdIns(4,5)P2 but not with Ins(1,4,5)P3. The acyl-modified PtdIns(4,5)P2 analog showed little protein labeling even at very low concentrations, whereas the head-group-modified PtdIns(4,5)P2 phosphotriester-labeled monomeric and oligomeric profilin. Mass spectroscopic analyses of CNBr digests of [3H]BZDC-Ins(1,4,5)P3-modified recombinant profilin suggested that modification was in the amino-terminal helical CNBr fragment. Edman degradation confirmed Ala1 of profilin I (residue 4 of the recombinant protein) was modified. Molecular models show a minimum energy conformation in which the hydrophobic region of the ligand contacts the amino-terminal helix whereas the 4,5-bisphosphate interacts with Arg135 and Arg136 of the carboxy-terminal helix. CONCLUSIONS: The PtdIns(4,5)P2-binding site of profilin I includes a bisphosphate interaction with a base-rich motif in the carboxy-terminal helix and contact between the lipid moiety of PtdIns(4,5)P2 and a hydrophobic region of the aminoterminal helix of profilin. This is the first direct evidence for a site of interaction of the lipid moiety of a phosphoinositide bisphosphate analog with profilin.

Binding Sites↗

PubMed1998

Comprehensive mutational analysis of the TSC1 gene: observations on frequency of mutation, associated features, and nonpenetrance.

We performed a comprehensive analysis for mutations in the TSC1 gene using Southern blot analysis, and SSCP and heteroduplex analysis of amplified exons in 13 families with genetic linkage to the TSC1 region, 22 small families without linkage information, and 126 sporadic patients. 17 unique mutations were identified in 21 patients. Mutations were found in 7/13 (54%) TSC1-linked families, 1/22 (5%) small families without linkage, and 13 of 126 (10%) sporadic cases. The mutations were all chain-terminating, with 14 small deletions, 1 small insertion, and 6 nonsense mutations. In families with mutations, all individuals carrying a mutation met formal diagnostic criteria for TSC, apart from a 3-year-old girl who had inherited a deletion mutation, and who had no seizures, normal intelligence, normal abdominal ultrasound, and hypomelanotic macules only on physical exam. We assessed the incidence and severity of mental retardation in the 13 sporadic patients with TSC1 mutations versus the entire sporadic cohort, and found no significant difference. The observations indicate that TSC1 mutations are all inactivating, suggest that TSC1 disease occurs in only 15-20% of the sporadic TSC population, and demonstrate that presymptomatic TSC does occur.

Adolescent↗

PubMed1998

Comprehensive mutation analysis of TSC1 using two-dimensional DNA electrophoresis with DGGE.

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterised by the development of benign tumors in multiple organs often causing serious neurologic impairment. To develop a reliable genetic test for TSC, two-dimensional electrophoresis with denaturing gradient gel electrophoresis (2D DGGE) has been developed to detect mutations in TSC1. The 23 exons of TSC1 were amplified using two rounds of PCR. In the first round, all coding regions of TSC1 were amplified in four fragments ranging in size from 7.4 kb to 9.9 kb. In the second round, 32 fragments representing 23 exons were amplified using primers designed to avoid overlapping fragments and with a GC clamp on one end to optimise melting characteristics. These exon fragments were then separated by size in the first dimension using a polyacrylamide gel, and by melting characteristics in the second dimension using a urea/formamide gradient to yield 32 distinct bands. If a mutation is present, four bands instead of one, are typically observed. During the development of this assay, we analysed 63 patient samples with known TSC1 mutations from prior studies. These 63 patients had 68 known mutations or polymorphisms. With DGGE, all 68 of these were identified (45 point mutations, 3 small insertions, 20 small deletions) and an additional 27 single base variants were discovered. To evaluate the assay, we analysed 19 of these samples in a blinded study. In the blinded analysis, 19/20 (95%) known mutations or polymorphisms were detected. The single missed mutation in the blinded analysis could be identified in retrospect and the assay was modified accordingly. During this study, we identified 2 new mutations (exon 8 and exon 15), a new polymorphism (intron 4), and the first variant identified in a non-coding exon (exon 2).

Base Sequence↗

PubMed1998

Molecular pathologic substaging in 244 stage I non-small-cell lung cancer patients: clinical implications.

PURPOSE: To retrospectively construct a comprehensive multivariate model of cancer recurrence and to design a molecular pathologic substaging system in stage I non-small-cell lung cancer (NSCLC). METHODS: All patients with stage I NSCLC resected at Brigham and Women's Hospital (Boston, MA) between 1984 and 1992 with adequate clinical follow-up were studied. The importance of three demographic characteristics, surgical extent, 11 pathologic features, and seven molecular factors on cancer-free survival was examined. RESULTS: Two hundred forty-four patients were studied, with 25 noncancer deaths and 80 patients with recurrent disease. Significant univariate predictors (P < .05) of cancer recurrence were age older than 60 years, male sex, wedge resection, World Health Organization (WHO) adenocarcinoma subtype solid tumor with mucin, lymphatic invasion, and p53 expression. Multivariate analysis identified nine independent predictors of recurrence: solid tumor with mucin, a wedge resection, tumor diameter of 4 cm or greater, lymphatic invasion, age older than 60 years, male sex, p53 expression, K-ras codon 12 mutation, and absence of H-ras p21 expression. Multivariate cancer-free survival (CFS) analysis in the 180 patients who underwent lobectomy or pneumonectomy led to the elimination of sex and age, which left six independent factors. CONCLUSION: Lobectomy or pneumonectomy should be performed in stage I NSCLC. Using the six independent factors for recurrent disease, we propose a pathologic molecular substaging system. Patients with two factors or less are graded Ia, with a 5-year CFS rate of 87%; those with three factors are graded Ib, with a 5-year CFS rate of 58%; and those with four factors or more are graded Ic, with a 5-year CFS rate of 21%.

Adult↗

PubMed1998

Advillin (p92): a new member of the gelsolin/villin family of actin regulatory proteins.

A new member of the gelsolin/villin family of actin regulatory proteins was initially identified by screening an adult murine brain cDNA library with a probe for bovine adseverin. The predicted amino acid sequence of the 92 kDa murine protein p92 (advillin) is 75% homologous to villin and 65% homologous to gelsolin and adseverin. It shares a six domain structure with other gelsolin family members and has a carboxy-terminal headpiece, similar to, yet distinct from, villin. Northern blot analysis shows a high level of mRNA expression in murine uterus and human intestine. In situ mRNA analysis of adult murine tissues demonstrates that the message is most highly expressed in the endometrium of the uterus, the intestinal lining, and at the surface of the tongue. In murine embryonic development, strong expression of the message is observed by day 14.5 in dorsal root ganglia and trigeminal ganglia. Expression is also noted at day 16.5 in cerebral cortex. We propose that p92 (advillin) has unique functions in the morphogenesis of neuronal cells which form ganglia, and that it may compensate to explain the near normal phenotype observed in villin-deficient mice.

Amino Acid Sequence↗

PubMed1998

EGF receptor regulation of cell motility: EGF induces disassembly of focal adhesions independently of the motility-associated PLCgamma signaling pathway.

A current model of growth factor-induced cell motility invokes integration of diverse biophysical processes required for cell motility, including dynamic formation and disruption of cell/substratum attachments along with extension of membrane protrusions. To define how these biophysical events are actuated by biochemical signaling pathways, we investigate here whether epidermal growth factor (EGF) induces disruption of focal adhesions in fibroblasts. We find that EGF treatment of NR6 fibroblasts presenting full-length WT EGF receptors (EGFR) reduces the fraction of cells presenting focal adhesions from approximately 60% to approximately 30% within 10 minutes. The dose dependency of focal adhesion disassembly mirrors that for EGF-enhanced cell motility, being noted at 0.1 nM EGF. EGFR kinase activity is required as cells expressing two kinase-defective EGFR constructs retain their focal adhesions in the presence of EGF. The short-term (30 minutes) disassembly of focal adhesions is reflected in decreased adhesiveness of EGF-treated cells to substratum. We further examine here known motility-associated pathways to determine whether these contribute to EGF-induced effects. We have previously demonstrated that phospholipase C(gamma) (PLCgamma) activation and mobilization of gelsolin from a plasma membrane-bound state are required for EGFR-mediated cell motility. In contrast, we find here that short-term focal adhesion disassembly is induced by a signaling-restricted truncated EGFR (c'973) which fails to activate PLCgamma or mobilize gelsolin. The PLC inhibitor U73122 has no effect on this process, nor is the actin severing capacity of gelsolin required as EGF treatment reduces focal adhesions in gelsolin-devoid fibroblasts, further supporting the contention that focal adhesion disassembly is signaled by a pathway distinct from that involving PLCgamma. Because both WT and c'973 EGFR activate the erk MAP kinase pathway, we additionally explore here this signaling pathway, not previously associated with growth factor-induced cell motility. Levels of the MEK inhibitor PD98059 that block EGF-induced mitogenesis and MAP kinase phosphorylation also abrogate EGF-induced focal adhesion disassembly and cell motility. In summary, we characterize for the first time the ability of EGFR kinase activity to directly stimulate focal adhesion disassembly and cell/substratum detachment, in relation to its ability to stimulate migration. Furthermore, we propose a model of EGF-induced motogenic cell responses in which the PLCgamma pathway stimulating cell motility is distinct from the MAP kinase-dependent signaling pathway leading to disassembly and reorganization of cell-substratum adhesion.

Animals↗

PubMed1998

Frequent progesterone receptor immunoreactivity in tuberous sclerosis-associated renal angiomyolipomas.

Angiomyolipomas can occur sporadically or in association with tuberous sclerosis complex (TSC). TSC is an autosomal dominant disorder characterized by seizures, mental retardation, and benign tumors of the brain, heart, kidney, and skin. Angiomyolipomas are more common in women than in men, suggesting a possible hormonal influence on tumor growth. In this study, 35 angiomyolipomas from 23 patients were immunostained with antibodies to estrogen receptor (ER) and progesterone receptor (PR). Eleven angiomyolipomas (31%) contained clusters of PR-immunoreactive smooth muscle cells. None contained ER-immunoreactive cells. Of the 21 tumors from patients with TSC, 11 (48%) were PR immunoreactive. All of the PR-immunoreactive angiomyolipomas were from women younger than 50 years of age, and all except one of these women had TSC. This study suggests that hormonal factors play a role in the pathogenesis of TSC-associated angiomyolipomas.

Adult↗

PubMed1997

The actin-severing protein gelsolin modulates calcium channel and NMDA receptor activities and vulnerability to excitotoxicity in hippocampal neurons.

Calcium influx through NMDA receptors and voltage-dependent calcium channels (VDCC) mediates an array of physiological processes in neurons and may also contribute to neuronal degeneration and death in neurodegenerative conditions such as stroke and severe epileptic seizures. Gelsolin is a Ca2+-activated actin-severing protein that is expressed in neurons, wherein it may mediate motility responses to Ca2+ influx. Primary hippocampal neurons cultured from mice lacking gelsolin exhibited decreased actin filament depolymerization and enhanced Ca2+ influx after exposure to glutamate. Whole-cell patch-clamp analyses showed that currents through NMDA receptors and VDCC were enhanced in hippocampal neurons lacking gelsolin, as a result of decreased current rundown; kainate-induced currents were similar in neurons containing and lacking gelsolin. Vulnerability of cultured hippocampal neurons to glutamate toxicity was greater in cells lacking gelsolin. Seizure-induced damage to hippocampal pyramidal neurons was exacerbated in adult gelsolin-deficient mice. These findings identify novel roles for gelsolin in controlling actin-mediated feedback regulation of Ca2+ influx and in neuronal injury responses. The data further suggest roles for gelsolin and the actin cytoskeleton in both physiological and pathophysiological events that involve activation of NMDA receptors and VDCC.

Actins↗

PubMed1997

Caspase-3-generated fragment of gelsolin: effector of morphological change in apoptosis.

The caspase-3 (CPP32, apopain, YAMA) family of cysteinyl proteases has been implicated as key mediators of apoptosis in mammalian cells. Gelsolin was identified as a substrate for caspase-3 by screening the translation products of small complementary DNA pools for sensitivity to cleavage by caspase-3. Gelsolin was cleaved in vivo in a caspase-dependent manner in cells stimulated by Fas. Caspase-cleaved gelsolin severed actin filaments in vitro in a Ca2+-independent manner. Expression of the gelsolin cleavage product in multiple cell types caused the cells to round up, detach from the plate, and undergo nuclear fragmentation. Neutrophils isolated from mice lacking gelsolin had delayed onset of both blebbing and DNA fragmentation, following apoptosis induction, compared with wild-type neutrophils. Thus, cleaved gelsolin may be one physiological effector of morphologic change during apoptosis.

Actins↗

PubMed1997

Delayed retraction of filopodia in gelsolin null mice.

Growth cones extend dynamic protrusions called filopodia and lamellipodia as exploratory probes that signal the direction of neurite growth. Gelsolin, as an actin filament-severing protein, may serve an important role in the rapid shape changes associated with growth cone structures. In wild-type (wt) hippocampal neurons, antibodies against gelsolin labeled the neurite shaft and growth cone. The behavior of filopodia in cultured hippocampal neurons from embryonic day 17 wt and gelsolin null (Gsn-) mice (Witke, W., A.H. Sharpe, J.H. Hartwig, T. Azuma, T.P. Stossel, and D.J. Kwiatkowski. 1995. Cell. 81:41-51.) was recorded with time-lapse video microscopy. The number of filopodia along the neurites was significantly greater in Gsn- mice and gave the neurites a studded appearance. Dynamic studies suggested that most of these filopodia were formed from the region of the growth cone and remained as protrusions from the newly consolidated shaft after the growth cone advanced. Histories of individual filopodia in Gsn- mice revealed elongation rates that did not differ from controls but an impaired retraction phase that probably accounted for the increased number of filopodia long the neutrite shaft. Gelsolin appears to function in the initiation of filopodial retraction and in its smooth progression.

Animals↗

PubMed1997

Human XPMC2H: cDNA cloning, mapping to 9q34, genomic structure, and evaluation as TSC1.

XPMC2 is a Xenopus gene identified on the basis of its ability to correct a mitotic defect in fission yeast. Here we report the identification of cDNA clones for human XPMC2H, its mapping to the tuberous sclerosis gene TSC1 region on 9q34, determination of genomic structure, and identification of several coding region polymorphisms. The predicted protein has strong sequence similarity to the Xenopus gene. Through SSCP and heteroduplex analysis of genomic DNA, we found two intragenic polymorphisms but no evidence for significant mutations in patients with tuberous sclerosis in this gene.

Chromosome Mapping↗

PubMed1997

Characterization of gelsolin truncates that inhibit actin depolymerization by severing activity of gelsolin and cofilin.

Gelsolin is a calcium-activated actin-binding protein with six subdomains. The N-terminal (G1) domain is essential for actin-filament-severing activity while other domains within G2-3 position the protein on the filament side allowing G1 to sever. In order to generate reagents capable of competitively inhibiting endogenous gelsolin and, potentially, other actin filament regulatory protein, we expressed several truncates of gelsolin in Escherichia coli, and analyzed how they affected the in vitro activity of two different actin-binding proteins, gelsolin and cofilin. A Ca2+-sensitive truncate containing G2-6 inhibited the F-actin-depolymerizing activities of both gelsolin and cofilin, while a G2-3 truncate was less effective. Using two independent assays, our results support the idea that gelsolin truncates inhibit actin filament severing and do not markedly affect actin subunit dissociation kinetics. Cosedimentation assays in the presence of calcium demonstrate that the G2-6 truncate binds to F-actin more strongly than the G2-3 truncate consistent with a protection mechanism by conformational change of F-actin and/or competitive binding to actin filaments which depends upon the presence of actin filament binding domains.

Actin Depolymerizing Factors↗

PubMed1997

Identification of the tuberous sclerosis gene TSC1 on chromosome 9q34.

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by the widespread development of distinctive tumors termed hamartomas. TSC-determining loci have been mapped to chromosomes 9q34 (TSC1) and 16p13 (TSC2). The TSC1 gene was identified from a 900-kilobase region containing at least 30 genes. The 8.6-kilobase TSC1 transcript is widely expressed and encodes a protein of 130 kilodaltons (hamartin) that has homology to a putative yeast protein of unknown function. Thirty-two distinct mutations were identified in TSC1, 30 of which were truncating, and a single mutation (2105delAAAG) was seen in six apparently unrelated patients. In one of these six, a somatic mutation in the wild-type allele was found in a TSC-associated renal carcinoma, which suggests that hamartin acts as a tumor suppressor.

Amino Acid Sequence↗

PubMed1997

Report on the Fifth International Workshop on Chromosome 9 held at Eynsham, Oxfordshire, UK, September 4-6, 1996.

The Fifth International workshop on chromosome 9 comprised a gathering of 36 scientists from seven countries and included a fairly even distribution of interests along chromosome 9 as well as a strong input from more global activities and from comparative mapping. At least eight groups had participated in the goal set at the previous workshop which was to improve the fine genetic mapping in different regions of chromosome 9 by meiotic breakpoint mapping in allocated regions and this has resulted in some greatly improved order information. Excellent computing facilities were available and all contributed maps were entered not only into SIGMA (and thence submitted to GDB) but also into a dedicated version of ACEDB which can be accessed on the Web in the form of one of 28 slices into which the chromosome has been arbitrarily divided. It was generally agreed that the amount of data is now overwhelming and that the integration and validation of all data is not only unrealistic in a short meeting but probably impossible until the whole chromosome has been sequenced and fully annotated. Sequence-ready contigs presented at the meeting totalled about 3 MB which is about one fiftieth of the estimated length. The single biggest barrier to integration of maps is the problem of non-standard nomenclature of loci. In the past 2 workshops efforts have been made to compare traditional 'consensus' maps made by human insight (still probably best for small specific regions) with those generated with some computer assistance (such as SIGMA) and those generated objectively by defined computer algorithms such as ldb. Since no single form of map or representation is entirely satisfactory for all purposes the maps reproduced in the published version of the report are confined to one of the genetic maps, in which Genethon and older markers have been incorporated, a Sigma map of the genes as symbols together with a listing of known 'disease' genes on chromosome 9, and a revised assessment of the mouse map together with a list of mouse loci predicted to be on human chromosome 9. One of the 28 ACEDB slices is also shown to illustrate strengths and weaknesses of this approach. Workshop files include not only all maps available at the time but also details of loci and details of the meiotic breakpoints in the CEPH families (http:/(/)www.gene.ucl.ac.uk/scw9db.shtml) .

Animals↗

PubMed1997

Cloning and evaluation of RALGDS as a candidate for the tuberous sclerosis gene TSC1.

RALGDS is a 115 kDa protein which was identified by its ability to enhance guanine nucleotide exchange for the ras family member ral. It also binds to activated ras and rap1, and appears to function as part of a signalling complex in downstream events following rap1 activation. Here we report the identification of full-length cDNA clones for human RALGDS, isolated from a brain cDNA library. The predicted protein has strong sequence homology to rat and murine isoforms of RALGDS in the N- and C-terminal regions, but an internal region (aa 250-380) shows relatively high divergence with only 42% identical amino acid residues. The human RALGDS gene is contained within a 30 kb region of 9q34, approximately 200 kb proximal to the ABO gene, within the current critical region for the tuberous sclerosis gene TSC1. Partial genomic structure was determined; it consists of at least 11 exons. Based upon analysis of Southern blots from 110 TSC patients, genomic DNA SSCP analysis, and RT-PCR analysis which demonstrated RNA expression of both alleles in patients from 9q34-linked TSC families using intragenic polymorphisms, we conclude that RALGDS is not likely to be TSC1.

Amino Acid Sequence↗