Murine adseverin (D5), a novel member of the gelsolin family, and murine adseverin are induced by interleukin-9 in T-helper lymphocytes

We identified a number of upregulated genes by differential screening of interleukin-9-stimulated T-helper lymphocytes. Interestingly, two of these messengers encode proteins that are similar to proteins of the gelsolin family. The first displays a typical structure of six homologous domains and shows a high level of identity (90%) with bovine adseverin (or scinderin) and may therefore be considered the murine adseverin homolog. The second encodes a protein with only five segments. Sequence comparison shows that most of the fifth segment and a short amino-terminal part of the sixth segment (amino acids 528 to 628 of adseverin) are missing, and thus, this form may represent an alternatively spliced product derived from the same gene. The corresponding protein is called mouse adseverin (D5). We expressed both proteins in Escherichia coli and show that mouse adseverin displays the typical characteristics of all members of the gelsolin family with respect to actin binding (capping, severing, and nucleation) and its regulation by Ca2+. In contrast, mouse adseverin (D5) fails to nucleate actin polymerization, although like mouse adseverin and gelsolin, it severs and caps actin filaments in a Ca2+-dependent manner. Adseverin is present in all of the tissues and most of the cell lines tested, although at low concentrations. Mouse adseverin (D5) was found only in blood cells and in cell lines derived from T-helper lymphocytes and mast cells, where it is weakly expressed. In a gel filtration experiment, we demonstrated that mouse adseverin forms a 1:2 complex with G actin which is stable only in the presence of Ca2+, while no stable complex was observed for mouse adseverin (D5).

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.

Gelsolin, a protein that caps the barbed ends and severs actin filaments, enhances the actin-based motility of Listeria monocytogenes in host cells

The actin-based motility of Listeria monocytogenes requires the addition of actin monomers to the barbed or plus ends of actin filaments. Immunofluorescence micrographs have demonstrated that gelsolin, a protein that both caps barbed ends and severs actin filaments, is concentrated directly behind motile bacteria at the junction between the actin filament rocket tail and the bacterium. In contrast, CapG, a protein that strictly caps actin filaments, fails to localize near intracellular Listeria. To explore the effect of increasing concentrations of gelsolin on bacterial motility, NIH 3T3 fibroblasts stably transfected with gelsolin cDNA were infected with Listeria. The C5 cell line containing 2.25 times control levels of gelsolin supported significantly higher velocities of bacterial movement than did control fibroblasts (mean +/- standard error of the mean, 0.09 +/- 0.003 micro(m)/s [n = 176] versus 0.05 +/- 0.003 micro(m)/s [n = 65]). The rate of disassembly of the Listeria-induced actin filament rocket tail was found to be independent of gelsolin content. Therefore, if increases in gelsolin content result in increases in Listeria-induced rocket tail assembly rates, a positive correlation between gelsolin content and tail length would be expected. BODIPY-phalloidin staining of four different stably transfected NIH 3T3 fibroblast cell lines confirmed this expectation (r = 0.92). Rocket tails were significantly longer in cells with a high gelsolin content. Microinjection of gelsolin 1/2 (consisting of the amino-terminal half of native gelsolin) also increased bacterial velocity by more than 2.2 times. Microinjection of CapG had no effect on bacterial movement. Cultured skin fibroblasts derived from gelsolin-null mice were capable of supporting intracellular Listeria motility at velocities comparable to those supported by wild-type skin fibroblasts. These experiments demonstrated that the surface of Listeria contains a polymerization zone that can block the barbed-end-capping activity of both gelsolin and CapG. The ability of Listeria to uncap actin filaments combined with the severing activity of gelsolin can accelerate actin-based motility. However, gelsolin is not absolutely required for the actin-based intracellular movement of Listeria because its function can be replaced by other actin regulatory proteins in gelsolin-null cells, demonstrating the functional redundancy of the actin system.

A cloning method for caspase substrates that uses the yeast two-hybrid system: cloning of the antiapoptotic gene gelsolin

Caspase-mediated proteolysis is a critical and central element of the apoptotic process; therefore, it is important to identify the downstream molecular targets of caspases. We established a method for cloning the genes of caspase substrates by two major modifications of the yeast two-hybrid system: (i) both large and small subunits of active caspases were expressed in yeast under ADH1 promoters and the small subunit was fused to the LexA DNA-binding domain; and (ii) a point mutation was introduced that substituted serine for the active site cysteine and thereby prevented proteolytic cleavage of the substrates, possibly stabilizing the enzyme-substrate complexes in yeast. After screening a mouse embryo cDNA expression library by using the bait plasmid for caspase-3, we obtained 13 clones that encoded proteins binding to caspase-3, and showed that 10 clones including gelsolin, an actin-regulatory protein implicated in apoptosis, were cleaved by recombinant caspase-3 in vitro. Using the same bait, we also isolated human gelsolin cDNA from a human thymus cDNA expression library. We showed that human gelsolin was cleaved during Fas-mediated apoptosis in vivo and that the caspase-3 cleavage site of human gelsolin was at D352 of DQTD352G, findings consistent with previous observations on murine gelsolin. In addition, we ascribed the antiapoptotic activity of gelsolin (which we previously reported) to prevention of a step leading to cytochrome c release from the mitochondria into the cytosol. Our results indicate that this cloning method is useful for identification of the substrates of caspases and possibly also of other enzymes.

Cells of the neuronal lineage play a major role in the generation of amyloid precursor fragments in gelsolin-related amyloidosis

Gelsolin-related amyloidosis or familial amyloidosis, Finnish type (FAF) (OMIM No105120) is a hereditary amyloid disease caused by a mutation in a precursor protein for amyloid (gelsolin) and characterized by corneal dystrophy and polyneuropathy. In vitro expression of the FAF-mutant (Asp187 --> Asn/Tyr) secretory gelsolin in COS cells leads to generation of an aberrant polypeptide presumably representing the precursor for tissue amyloid. Here, we provide evidence that this abnormal processing results from defective initial folding of the secreted FAF gelsolin due to the lack of the Cys188-Cys201 disulfide bond, normally formed next to the FAF mutation site. We compared cells of different tissue origin and discovered a dramatic difference between the amount of cleavage of FAF gelsolin to the amyloid precursor in neuronal and non-neuronal cells. More than half of the mutant gelsolin was cleaved in PC12 and in vitro differentiated human neuronal progenitor cells. In contrast, human fibroblasts and Schwannoma cell cultures showed only a limited capacity to cleave FAF gelsolin, although the cleavage mechanism per se seems to be similar in the various cell types. The present findings of processing and distribution of secreted FAF gelsolin in the neuronal cells emphasize the role of neurons in the tissue pathogenesis of this amyloid polyneuropathy.

Identification of the binding partners for flightless I, A novel protein bridging the leucine-rich repeat and the gelsolin superfamilies

Flightless-I (fliI) is a novel member of the gelsolin family that is important for actin organization during Drosophila embryogenesis and myogenesis. Drosophila fliI and the human homolog FLI both contain the classic gelsolin 6-fold segmental repeats and an amino-terminal extension of 16 tandem leucine-rich repeats (LRR). LRR repeats form amphipathic beta-alpha structural units that mediate protein-protein interactions. Although there are close to 100 known LRR domain-containing proteins, only a few binding pairs have been identified. In this paper, we used biochemical and genetic approaches to identify proteins that interact with human FLI. In vitro synthesized FLI bound to actin-Sepharose and binding was reduced by competition with excess soluble actin. Actin binding was mediated through the gelsolin-like domain and not the LRR domain. Although the FLI LRR module is most closely related to the LRR domains of Ras-interactive proteins, FLI does not associate with Ras, selected Ras effectors, or other Ras-related small GTPases. Two-hybrid screens using FLI LRR as bait identified a novel LRR binding partner. The 0.65-kilobase pair (kb) clone from the screen survived additional rounds of stringent two-hybrid pairwise assays, establishing a specific interaction. Binding to FLI LRR was corroborated by co-immunoprecipitation with FLI LRR. The translated sequence of the FLI LRR associated protein (FLAP) encodes a novel protein not represented in the data base. Northern blot analyses revealed four FLAP messages of approximately 2.7, 2.9, 3.3, and 5.1 kb, which are differentially expressed in the tissues tested. Skeletal and cardiac muscles are particularly rich in the 3.3-kb FLAP message, and the FLI message as well. Full-length FLAP clones were isolated from a mouse skeletal muscle cDNA library. They have an open reading frame which encodes for a protein containing 626 amino acids. Sequence analyses predict that the FLAP protein is rich in alpha-helices and contains stretches of dimeric coiled coil in its middle region and COOH terminus. The identification of actin and FLAP as the binding ligands for the gelsolin-like domain and the LRR domain, respectively, suggests that FLI may link the actin cytoskeleton to other modules implicated in intermolecular recognition and structural organization.

Functional characteristics and the complete primary structure of ascidian gelsolin

The body wall of the ascidian is composed of unusual multi-nucleated smooth muscle cells enriched with thin actin filaments containing troponin-tropomyosin which run along the longitudinal cell axis without being organized into striated structures. We purified an actin-binding protein of 80 kDa, tentatively termed 80K protein, from the body wall muscle of ascidian, Halocynthia roretzi, and characterized the functional properties and molecular structures. In the presence of Ca2+, the 80K protein accelerated the initial phase of actin polymerization, namely the nucleation process, decreased the level of polymerization at the steady state, caused marked reduction in viscosity of an F-actin solution, and fragmented F-actin filaments, while in the absence of Ca2+, it remained associated with F-actin without severing the filaments. The interaction of the 80K protein with actin was inhibited by phosphatidylinositol 4,5-bisphosphate (PIP2). When actin was polymerized in the presence of acrosome actin bundles from horseshoe crab sperm, the 80K protein inhibited the growth of actin filaments at the barbed end but not at the pointed end, indicating that the 80K protein functions as a barbed-end capping protein. In order to characterize the molecular structure of the 80K protein, cDNAs encoding this protein were isolated from the lambda gt11 cDNA library of the ascidian muscle by using a monoclonal antibody (AS23) specific for this protein and the entire sequence was determined. The deduced peptide sequence showed about 44% homology in amino acid residues with the human gelsolin sequence, and in addition, 6 repeating segments were observed in the sequence of the 80K protein as has been described in the gelsolin sequence. These results indicate strongly that the 80K protein belongs to the gelsolin family.

Equus caballus gelsolin--cDNA sequence and protein structural implications

We have generated and characterized the cDNA from equine smooth muscle that encodes gelsolin, an actin-modulating protein. Overlapping cDNA clones synthesized by the reverse transcriptase/polymerase chain reaction and clones isolated from a horse genomic library provided the complete primary structure for the intracellular isoform of gelsolin, while cDNA complemented with protein sequence data produced the full-length primary transcript of the gelsolin isoform found circulating in equine plasma. The deduced amino acid sequences of the intracellular and secreted versions of equine gelsolin infer polypeptides of 731 and 755 residues with apparent molecular masses of 80.7 kDa and 83.2 kDa, respectively. Multiple sequence alignment analysis of equine, human, porcine, and murine orthologs of gelsolin demonstrates prominent similarities among all of these proteins, with the horse and human molecules exhibiting the largest degree of likeness with respect to polypeptide length and overall sequence composition. Both horse and human plasma gelsolins are comprised of 755 amino acids with 94% of the residues identical, while the degree of sequence identity in the shorter (731 residues) cytoplasmic gelsolins is 95%. Analysis of the sequences and structures of the six related domains that comprise gelsolin emphasizes the strong correlation that exists between primary structural conservation among mammalian gelsolins and maintenance of the three-dimensional domain fold characteristic of members of this protein family.

Frequent loss of gelsolin expression in non-small cell lung cancers of heavy smokers

Most lung and bladder cancers have been shown to be associated with smoking. We have previously demonstrated the frequent loss of gelsolin expression and its tumor suppressor activity in bladder cancer (M. Tanaka et al., Cancer Res., 55: 3228-3232, 1995). Here, we examined gelsolin expression in 12 cultured non-small cell lung cancer (NSCLC) cell lines. Furthermore, we analyzed gelsolin expression in relation to patients' smoking habits in 88 surgically resected NSCLCs to investigate whether gelsolin could be a molecular target for tobacco-induced carcinogenesis of lung cancer. All 12 NSCLC cell lines showed low-to-undetectable expression of the gelsolin gene, compared to that in normal lung tissue, by Northern blot analysis. On the other hand, Southern blot analysis of genomic DNA did not show any gross rearrangements or deletions of the gene in the NSCLC cell lines. Western blot analysis of gelsolin expression showed low-to-undetectable gelsolin expression in all 12 NSCLC cell lines, compared to normal lung tissue. Immunocytochemical analysis of gelsolin expression in NSCLC cell lines showed results that were consistent with those obtained by Western blot analysis, using normal bronchial epithelial cells as a positive control: two cell lines with lower gelsolin expression by Western blot analysis had reduced but positive cytoplasmic immunostaining of gelsolin, compared with primary normal bronchial epithelial cells, whereas no such immunostaining was observed in two cell lines with much lower or undetectable gelsolin expression by Western blot analysis. Therefore, gelsolin expression was analyzed in surgically resected NSCLCs by immunohistochemistry. Reduced or undetectable gelsolin expression was observed in 48 of 88 (55 %) resected NSCLCs. Such altered gelsolin expression significantly correlated with heavy smoking of patients (> or =20 pack-years; P = 0.008 by the chi2 test and P = 0.03 by multivariate logistic regression analysis), whereas there was no significant correlation between gelsolin expression and histological type, pathological tumor-node-metastasis (pTNM) stage, or survival. These findings suggest that the frequent loss of gelsolin expression may be involved in the development of NSCLCs as a potential molecular target of tobacco-induced carcinogenesis.

Supervillin (p205): A novel membrane-associated, F-actin-binding protein in the villin/gelsolin superfamily

Actin-binding membrane proteins are involved in both adhesive interactions and motile processes. We report here the purification and initial characterization of p205, a 205-kD protein from bovine neutrophil plasma membranes that binds to the sides of actin filaments in blot overlays. p205 is a tightly bound peripheral membrane protein that cosediments with endogenous actin in sucrose gradients and immunoprecipitates. Amino acid sequences were obtained from SDS-PAGE-purified p205 and used to generate antipeptide antibodies, immunolocalization data, and cDNA sequence information. The intracellular localization of p205 in MDBK cells is a function of cell density and adherence state. In subconfluent cells, p205 is found in punctate spots along the plasma membrane and in the cytoplasm and nucleus; in adherent cells, p205 concentrates with E-cadherin at sites of lateral cell-cell contact. Upon EGTA-mediated cell dissociation, p205 is internalized with E-cadherin and F-actin as a component of adherens junctions "rings." At later times, p205 is observed in cytoplasmic punctae. The high abundance of p205 in neutrophils and suspension-grown HeLa cells, which lack adherens junctions, further suggests that this protein may play multiple roles during cell growth, adhesion, and motility. Molecular cloning of p205 cDNA reveals a bipartite structure. The COOH terminus exhibits a striking similarity to villin and gelsolin, particularly in regions known to bind F-actin. The NH2 terminus is novel, but contains four potential nuclear targeting signals. Because p205 is now the largest known member of the villin/gelsolin superfamily, we propose the name, "supervillin." We suggest that supervillin may be involved in actin filament assembly at adherens junctions and that it may play additional roles in other cellular compartments.

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.

Identification of the circulating amyloid precursor and other gelsolin metabolites in patients with G654A mutation in the gelsolin gene (Finnish familial amyloidosis): pathogenetic and diagnostic implications

Familial amyloidosis of the Finnish type (FAF) is an autosomal dominant type of systemic amyloidosis caused by a G654A (Asn-187) or G654T (Tyr-187) mutation in the gelsolin gene. Herein we show that patients with the Asn-187 gelsolin mutation have, in addition to full-sized gelsolin, a series of lower-Mr C-terminal fragments of gelsolin (Mr of 70,000-45,000) in the circulation, and that a 50 to 55-kd fragment of gelsolin is excreted in the urine. In homozygous FAF (Asn-187), the 65-kd fragment, which contains the amyloid-forming region (Ala173-Met243), and the 55-kd fragment, which is devoid of that region, are the major gelsolin species in plasma; whereas normal gelsolin, as well as a 70-kd fragment identified as the C-terminal portion of gelsolin starting at Glu122, and a 45-kd fragment starting at Ser384, are minor components. In patients heterozygous for the Asn-187 mutation--the usual form of the expression of the dominant disease--normal-sized gelsolin is the major circulating form; the 65- and 55-kd fragments represent minor components. Immunodetection of the plasma 65-kd gelsolin fragment, which is disease-specific, and measurement of the urinary gelsolin fragment provide useful means for diagnosing FAF.

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.

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.

[Tumor suppressive function of gelsolin]

We examined the expression of gelsolin in a murine ras tumor and a number of human stomach, colon, bladder, and lung cancer cell lines and tissues. In most of the cell lines and tumor tissues, gelsolin expression was undetectable or extremely low in comparison with its expression in normal epithelial cells. Upon the introduction of the exogenous human wild-type gelsolin cDNA into human cancer cell lines, the gelsolin transfectants had greatly reduced colony-forming ability and tumorigenicity in vivo. After UVC irradiation, the gelsolin-overexpressing bladder cancer cells demonstrated increased accumulation and/or protracted delay in G2 phase as compared to neotransfected cells. UVC-induced production of diacylglycerol was reduced in gelsolin-overexpressed UMUC-2 cells as compared to neo-transfected UMUC-2 cells. Levels of cyclin B in the synchronized and gelsolin-overexpressing UMUC-2 cells remained low during the G2 delay. To investigate the in vivo efficacy of gene therapy with the gelsolin tumor suppressor, we treated human urinary bladder cancers (UMUC-2 and DAB-1), inoculated in nude mice, with recombinant retrovirus packaging cells containing the human gelsolin cDNA. This gene therapy resulted in remarkable tumor growth inhibition, and prolonged survival time in the majority of animals. These observations suggest that gelsolin plays a key role as a tumor suppressor by regulating a G2 checkpoint function of cancer cells through phosphoinositol lipid metabolism, and demonstrate the potential of using the gelsolin tumor suppressor in human urinary bladder carcinoma.

A novel gelsolin isoform expressed by oligodendrocytes in the central nervous system

Two isoforms of the Ca2+-sensitive, actin-binding protein gelsolin have been identified thus far; one is an intracellular protein, cytoplasmic gelsolin, and the other is a secretory protein called plasma gelsolin. Gelsolin expression in the mammalian CNS appears to be localized mainly to oligodendrocytes where it is presumed that the cytoplasmic isoform predominates. Here, we show that oligodendrocytes not only contain cytoplasmic gelsolin, but they also express a novel gelsolin isoform that we have named gelsolin-3. Cytoplasmic gelsolin, plasma gelsolin, and gelsolin-3 arise by alternative splicing from the same gene. The N-terminal amino acid sequence unique to gelsolin-3 is shown to be encoded by a single exon in a region previously thought to be an intron in the human gelsolin gene. In situ hybridization analysis confirmed that gelsolin-3 mRNA is localized primarily to oligodendrocytes in rat brain. In other tissues, gelsolin-3 shows a more restricted pattern of expression than cytoplasmic gelsolin. These data support the view that the gelsolin isoforms have differential roles in the regulation of the actin cytoskeleton.

Inhibition of apoptosis by the actin-regulatory protein gelsolin

Gelsolin is an actin-regulatory protein that modulates actin assembly and disassembly, and is believed to regulate cell motility in vivo through modulation of the actin network. In addition to its actin-regulatory function, gelsolin has also been proposed to affect cell growth. Our present experiments have tested the possible involvement of gelsolin in the regulation of apoptosis, which is significantly affected by growth. When overexpressed in Jurkat cells, gelsolin strongly inhibited apoptosis induced by anti-Fas antibody, C2-ceramide or dexamethasone, without changing the F-actin morphology or the levels of Fas or Bcl-2 family proteins. Upon the induction of apoptosis, an increase in CPP32(-like) protease activity was observed in the control vector transfectants, while it was strongly suppressed in the gelsolin transfectants. Pro-CPP32 protein, an inactive form of CPP32 protease, remained uncleaved by anti-Fas treatment in the gelsolin transfectants, indicating that gelsolin blocks upstream of this protease. The tetrapeptide inhibitor of CPP32(-like) proteases strongly inhibited Fas-mediated apoptosis, but only partially suppressed both C2-ceramide- and dexamethasone-induced apoptosis. These data suggest that the critical target responsible for the execution of apoptosis may exist upstream of CPP32(-like) proteases in Jurkat cells and that gelsolin acts on this target to inhibit the apoptotic cell death program.

Genomic structure, evolution, and expression of human FLII, a gelsolin and leucine-rich-repeat family member: overlap with LLGL

The Drosophila melanogaster flightless-I gene is involved in cellularization processes in early embryogenesis and in the structural organization of indirect flight muscle. The encoded protein contains a gelsolin-like actin binding domain and an N-terminal leucine-rich repeat protein-protein interaction domain. The homologous human FLII gene encodes a 1269-residue protein with 58% amino acid sequence identity and is deleted in Smith-Magenis syndrome. We have cloned the FLII gene and determined its nucleotide sequence (14.1 kb). FLII has 29 introns, compared with 13 in Caenorhabditis elegans and 3 in D. melanogaster. The positions of several introns are conserved in FLII-related genes and in the domains and subdomains of the gelsolin-like regions giving indications of gelsolin gene family evolution. In keeping with its function in indirect flight muscle in Drosophila, the human FLII gene was most highly expressed in muscle. The FLII gene lies adjacent to LLGL, the human homologue of the D. melanogaster tumor suppressor gene lethal(2) giant larvae. The 3' end of the FLII transcript overlaps the 3' end of the LLGL transcript, and the corresponding mouse genes Fliih and Llglh also overlap. The overlap region contains poly(A) signals for both genes and is strongly conserved between human and mouse.

Analysis of an expression profile of genes in the human adipose tissue

Increasing evidence suggests that in addition to storing excess energy as fat, adipose tissue acts as an endocrine organ secreting various factors into the blood stream. Every time a new factor is found in adipose tissue, however, its implication is discussed independently, and a systematic analyses based upon a global view of gene expression of this tissue has not been performed. To describe the function of this tissue in terms of gene expression, and to find new factors, we performed random complementary DNA (cDNA) sequencing using a 3'-directed cDNA library that faithfully represents the composition of the messenger RNA (mRNA). Various well-known but unexpected genes, including those for gelsolin, plasma glutathione peroxidase (GPX-3) and carboxypeptidase E (CPE) were shown to be very active. By comparing the expression profile of active genes in the adipose with those of other tissues and with data in dbEST, we identified seven new genes that are specifically expressed in adipose tissue. Among these, one encoded a protein with collagen-like repeats and a putative secretion signal. These data can be used as new tools for analyses of the physiology of this tissue, as well as the etiology and complications of obesity.

Tissue distribution and levels of gelsolin mRNA in normal individuals and patients with gelsolin-related amyloidosis

We measured quantitatively the mRNA levels of intracellular and secretory forms of gelsolin, an actin-modulating protein, in human tissues from subjects of different ages. The intracellular gelsolin mRNA constituted the major type of gelsolin steady-state mRNA in all tissues analyzed. Both forms of gelsolin were expressed in most adult tissues, with particularly high mRNA levels in all types of muscle and interestingly in skin. Between the adult and infantile tissues the most striking difference in expression levels was found in liver, as the adult liver contained only a subtle amount of gelsolin mRNA. Skin and muscle samples from patients with gelsolin-related amyloidosis (FAF), with significantly increased concentrations of serum gelsolin, did not reveal an increased expression of the gene, and both mutant and wild-type alleles were expressed in equal amounts. The high level of expression of the gelsolin gene in the skin in general could locally contribute to the characteristic skin amyloidosis in FAF patients.

Widespread loss of gelsolin in breast cancers of humans, mice, and rats

Down-regulation of gelsolin, an actin-binding protein, is frequently found in several types of transformed cells and tumors. The present study demonstrates that gelsolin protein and RNA were absent or markedly reduced in human breast cancer cell lines relative to "normal" mortal human mammary epithelial cells and benign, immortalized cell lines. Moreover, actin filaments were usually attenuated coincident with the reduction in gelsolin. Gelsolin was also missing or greatly decreased in 70% of 30 human sporadic, invasive breast carcinomas examined by immunocytochemistry and in 100% of virally induced mouse and chemically induced rat mammary carcinomas evaluated by Northern analysis. Southern analysis revealed no major mutations in the gelsolin gene of human breast cancer cells. Our results show that partial or total loss of gelsolin expression is common to the majority of breast cancers of diverse etiologies in three animal species and point to gelsolin as a candidate suppressor of breast cancer.

In vitro expression analysis shows that the secretory form of gelsolin is the sole source of amyloid in gelsolin-related amyloidosis

Amyloidoses are a group of diseases where abnormal fibrillar protein deposits accumulate in patients' tissues. In familial amyloidosis of the Finnish type (FAF), or gelsolin-related amyloidosis, the amyloid subunit protein consists of gelsolin peptides of amino acids 173-243 with the disease causing substitution at Asp187. Gelsolin is an actin-modulating protein and exists in both secretory and intracellular forms both encoded by a single gene in chromosome 9. We have previously shown that the FAF-associated forms of secretory gelsolin carrying the Asp187Asn or Asp187Tyr mutations are abnormally processed in cells, resulting in the secretion of an aberrant 68 kDa carboxyterminal fragment. Here we demonstrate by N-terminal sequencing that the amino terminus of this abnormal fragment is the amino acid 173 and thus represents the N-terminus of the FAF amyloid. We also provide evidence that the same truncated gelsolin can be found among the aberrant gelsolin fragments detected in patients' CSF. Finally, we also expressed the FAF-associated forms of intracellular gelsolin in COS-1 cells, and found no abnormality in their processing opposite to secretory form. Our results provide strong evidence that the secretory gelsolin is solely responsible for the amyloid formation in FAF.

[Familial amyloidosis, Finnish type with marked anhidrosis]

Familial amyloidosis, Finnish type (FAF), is a gelsolin-related systemic amyloidosis that has an autosomal-dominant inheritance pattern and is clinically characterized by progressive cranial neuropathy, corneal lattice dystrophy and skin changes such as cutis laxa, blepharochalasis, and lichen amyloidosis. A 70-year-old Japanese male proband, who was believed to be originally from Fukuoka Prefecture, showed signs and symptoms characteristic of FAF. In addition, he complained of progressive anhidrosis and heat intolerance during the daytime in summer. On examination, perspiration was absent on the almost entire body surface. Molecular genetic studies showed a G-to-A transversion that resulted in the substitution of asparagine for aspartic acid 187 in the gelsolin gene, a mutation found in most patients with FAF. Skin biopsy revealed marked deposition of amyloid, which was positive with anti-gelsolin antibody staining, around eccrine sweat glands and ducts, and around sebaceous glands, outside the basal lamina; slight to mild deposition around small vessels and small nerve fascicles; and very slight deposition in the perineurium and endoneurium. Morphometric evaluation of the nerve terminals and axons of eccrine sweat glands revealed a significant decrease in the number of nerve terminals per transverse profile of the sweat gland. Compared with controls, nerve terminals were further from the secretory epithelial cell owing to deposition of amyloid outside its basal lamina. The proband's sister had almost identical, although much less severe, clinical signs and symptoms with the same mutation of the gelsolin gene. Autonomic signs and symptoms in FAF are reported to be less frequent and less severe than those in familial amyloid polyneuropathy of Andrade type. Findings in our proband suggest that perspiration may be markedly decreased in FAF owing to marked deposition of amyloid around the eccrine sweat gland which causes degeneration of the nerve terminals and disturbs access of the neurotransmitter to the secretory epithelial cell.

Thirteen loci physically assigned to sheep chromosome 2 by cell hybrid analysis and in situ hybridization

Sheep x hamster cell hybrids containing sheep metacentric Chromosome (Chr) 2 were produced by fusing blood leukocytes from normal sheep with hamster auxotrophic Ade F-minus mutants. Cell clones that were isocitrate dehydrogenase 1 (IDH1) positive were cytogenetically characterized, confirming that they contained sheep Chr 2. The following loci were newly assigned by Southern hybridization to sheep Chr 2: lipoprotein lipase (LPL), glycoprotein-4-beta galactosyltransferase 2 (GGTB2), neurofilament light polypeptide (68 kDa; NEFL), surfactant-associated protein 2 (SFTP2), lymphocyte-specific protein tyrosine kinase (LCK), and nebulin (NEB). These new assignments and the in situ localization of gelsolin (GSN) to sheep Chr 2pter-p24 are consistent with the predicted homology of cattle Chr 8 (U18) with sheep Chr 2p, and of cattle Chr 2 (U17) with sheep 2q. In addition, the assignment by cell hybrid analysis of loci previously mapped to Chr 2 in sheep, viz., cholinergic receptor, nicotinic, delta polypeptide (CHRND), collagen type III alpha 1 (COL3A1), fibronectin 1 (FN1), isocitrate dehydrogenase (IDH1), and villin 1 (VIL1), confirmed the localization of sheep syntenic group U11 to this chromosome. By nutritional selection and complementation of the hamster auxotrophic Ade F mutation, the multifunctional enzyme locus phosphoribosylaminoimidazolecarboxamide formyltransferase (AICAR transformylase)/IMP cyclohydrolase (inosinicase) (provisionally given the symbol PRACFT) has also been newly assigned to sheep Chr 2. This report significantly extends the number of loci physically mapped to sheep Chr 2 and confirms its close homology with cattle Chrs 2 and 8.