Emerging paradigms of integrin ligand binding and activation

Adhesion of cells to each other or to the extracellular matrix provides essential signals that regulate many cellular functions including cell migration, proliferation, differentiation and apoptosis. The integrin superfamily orchestrates many of these complex adhesive events through regulated interactions with a large variety of ligands. Crystallization of some ligands and of a ligand-binding integrin domain, reviewed here, together with extensive mutagenesis studies are beginning to shed light on the inner workings of these receptors.

Integrin-ligand interactions: scratching the surface

Integrins provide cells with critical means of communication with their microenvironments. By linking events at the cell surface to a dynamic cytoskeleton-signaling complex, integrins enable cells to rapidly modify their mechanical and genetic machinery in response to environmental cues. This review highlights major advances made in understanding the structural basis of integrin-ligand interactions and their regulation.

Induction of the CD11b gene during activation of the monocytic cell line U937 requires a novel nuclear factor MS-2

The differentiation of myeloid precursors into mature myelomonocytic cells is characterized by the induction of the gene encoding the beta2 integrin CD11b. The transcription factors Sp1 and PU.1 prime the CD11b promoter, but the nature of the factors responsible for its inducible expression are unknown. In addition to the CD11b gene, the homologous genes encoding CD11a and CD11c also exhibit inducible expression during myeloid differentiation. Therefore, we compared the nucleotide sequences of the CD11a, CD11b, and CD11c gene promoters to identify common elements that might contribute to inducible expression. This analysis identified one such element repeated four times within the CD11b promoter. Mutation of these elements indicated that two, MS-2beta and MS-2gamma, are critical to the induction of the CD11b gene during differentiation of the pro-monocytic cell line U937. Electrophoretic mobility shift assays indicate that MS-2beta and MS-2gamma interact with nuclear factors that are induced during U937 differentiation. These factors are detected at the time the CD11b promoter is activated. The molecular mass of these factors is approximately 28 kDa, and their DNA binding characteristics are indistinguishable from those of the novel nuclear factor MS-2. Taken together, our data indicate that MS-2 mediates induction of the CD11b gene as cells of the monocytic lineage mature. The presence of multiple potential binding sites for MS-2 in the promoter regions of a wide range of genes expressed in mature myeloid cells suggests this factor plays a general role in myeloid differentiation.

Induction of the CD11b gene during activation of the monocytic cell line U937 requires a novel nuclear factor MS-2

The differentiation of myeloid precursors into mature myelomonocytic cells is characterized by the induction of the gene encoding the beta2 integrin CD11b. The transcription factors Sp1 and PU.1 prime the CD11b promoter, but the nature of the factors responsible for its inducible expression are unknown. In addition to the CD11b gene, the homologous genes encoding CD11a and CD11c also exhibit inducible expression during myeloid differentiation. Therefore, we compared the nucleotide sequences of the CD11a, CD11b, and CD11c gene promoters to identify common elements that might contribute to inducible expression. This analysis identified one such element repeated four times within the CD11b promoter. Mutation of these elements indicated that two, MS-2beta and MS-2gamma, are critical to the induction of the CD11b gene during differentiation of the pro-monocytic cell line U937. Electrophoretic mobility shift assays indicate that MS-2beta and MS-2gamma interact with nuclear factors that are induced during U937 differentiation. These factors are detected at the time the CD11b promoter is activated. The molecular mass of these factors is approximately 28 kDa, and their DNA binding characteristics are indistinguishable from those of the novel nuclear factor MS-2. Taken together, our data indicate that MS-2 mediates induction of the CD11b gene as cells of the monocytic lineage mature. The presence of multiple potential binding sites for MS-2 in the promoter regions of a wide range of genes expressed in mature myeloid cells suggests this factor plays a general role in myeloid differentiation.

A novel role for the beta 2 integrin CD11b/CD18 in neutrophil apoptosis: a homeostatic mechanism in inflammation

In mice selectively deficient in CD11b/CD18, a beta 2 integrin, chemoattractant-induced leukocyte adhesion to microvascular endothelium in vivo was reduced. Paradoxically, thioglycollate-induced neutrophil accumulation in the peritoneal cavity was increased and was associated with a significant delay in apoptosis of extravasated cells. The extravasated cells had a near absence of neutrophil phagocytosis and a reduction in oxygen free radical generation, which may contribute to the observed defect in apoptosis. This is supported by our in vitro studies, in which phagocytosis of opsonized particles by human neutrophils rapidly induced apoptosis that could be blocked with CD11b/ CD18 antibodies. Reactive oxygen species are the intracellular link in this process: phagocytosis-induced apoptosis was blocked both in neutrophils treated with the flavoprotein inhibitor diphenylene iodonium and in neutrophils from patients with chronic granulomatous disease, which lack NADPH oxidase. Thus, CD11b/CD18 plays a novel and unsuspected homeostatic role in inflammation by accelerating the programmed elimination of extravasated neutrophils.

Characterization and cell distribution of polycystin, the product of autosomal dominant polycystic kidney disease gene 1

BACKGROUND

In a majority of cases, autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations within a putative open reading frame of the PKD1 gene. The encoded protein, polycystin, is predicted to span the plasma membrane several times and contains extracellular domains, suggestive of a role in cell adhesion. The cellular distribution and function of polycystin is not known.

MATERIALS AND METHODS

We selected as immunogens two conserved 15 amino acid peptides: P1, located in a predicted extracellular region of polycystin, and P2, located in the C-terminal putative cytoplasmic tail. The anti-peptide antibodies from immunized rabbits were affinity purified on peptide-coupled resins and their specificity confirmed by their selective binding to recombinant polycystin fusion proteins. Western blotting and immunohistochemistry were used to characterize the size, tissue, and cell distribution of polycystin.

RESULTS

A high-molecular mass protein (about 642 kD) was detected by Western blotting in rat brain tissue. A few additional bands, in the 100- to 400-kD range, probably representing tissue-specific variants and/or proteolytic fragments, were recognized in human and rat tissues. Polycystin was abundantly expressed in fetal kidney epithelia, where it displayed basolateral and apical membrane distribution in epithelial cells of the ureteric buds, collecting ducts, and glomeruli. In normal human adult kidney, polycystin was detected at moderate levels and in a cell surface-associated distribution in cortical collecting ducts and glomerular visceral epithelium. Expression of polycystin was significantly increased in cyst-lining epithelium in ADPKD kidneys, but was primarily intracellular.

CONCLUSIONS

Polycystin appears to be a developmentally regulated and membrane-associated glycoprotein. Its intracellular localization in the cyst-lining epithelium of ADPKD kidneys suggests an abnormality in protein sorting in this disease.

Solvent-accessible residues on the metal ion-dependent adhesion site face of integrin CR3 mediate its binding to the neutrophil inhibitory factor

Neutrophil adhesion-dependent functions such as chemotaxis, spreading, and phagocytosis are inhibited by neutrophil inhibitory factor (NIF), a glycoprotein produced by the hookworm Ancylostoma caninum. The NIF binding site has been localized to the A-domain of integrin CR3 (CD11b/CD18) and shown to be metal-dependent. The recently solved crystal structure of the A-domain from CD11b revealed a putative metal ion-dependent adhesion site (MIDAS) on the top of the structure. To determine if NIF binds to the A-domain at its MIDAS face, amino acid substitutions involving 24 residues present in surface loops and adjacent helices in the structure were created. The expressed CD11b A-domain and CR3 heterodimers were then tested in a blinded manner for their ability to bind to biotinylated NIF. The solvent-exposed Gly143, Asp149, Glu178-Glu179, and Arg208, all located on the MIDAS face, in close proximity to the metal ion, were involved in CR3-NIF interaction. These data show that the natural integrin antagonist, NIF, binds to CR3 through the MIDAS region and identify putative contact residues in this region that could be targeted therapeutically.

Congenital adrenal hyperplasia due to 11-beta-hydroxylase deficiency with skeletal abnormalities

Classic congenital 11-beta-hydroxylase deficiency is a relatively uncommon cause of congenital adrenal hyperplasia and is characterized by virilization and often hypertension. The association of skeletal abnormalities (short metatarsal bone) and pulmonary stenosis in a patient with 11-beta-hydroxylase has been reported by our group. In this report, three new patients with congenital adrenal hyperplasia due to a defect in 11-beta-hydroxylase enzyme with short fourth metatarsals are described. Gynecomastia was noted in one patient. The relative rarity of 11-beta-hydroxylase deficiency and the association of skeletal abnormalities suggest the possibility that this is more than a mere coincidental finding.

Two conformations of the integrin A-domain (I-domain): a pathway for activation?

BACKGROUND

Integrins are plasma membrane proteins that mediate adhesion to other cells and to components of the extracellular matrix. Most integrins are constitutively inactive in resting cells, but are rapidly and reversibly activated in response to agonists, leading to highly regulated cell adhesion. This activation is associated with conformational changes in their extracellular portions, but the nature of the structural changes that lead to a change in adhesiveness is not understood. The interactions of several integrins with their extracellular ligands are mediated by an A-type domain (generally called the I-domain in integrins). Binding of the I-domain to protein ligands is dependent on divalent cations. We have described previously the structure of the I-domain from complement receptor 3 with bound Mg2+, in which the glutamate side chain from a second I-domain completes the octahedral coordination sphere of the metal, acting as a ligand mimetic.

RESULTS

We now describe a new crystal form of the I-domain with bound Mn2+, in which water completes the metal coordination sphere and there is no equivalent of the glutamate ligand. Comparison of the two crystal forms reveals a change in metal coordination which is linked to a large (10 A) shift of the C-terminal helix and the burial of two phenylalanine residues into the hydrophobic core of the Mn2+ form. These structural changes, analogous to those seen in the signal-transducing G-proteins, alter the electrophilicity of the metal, reducing its ability to bind ligand-associated acidic residues, and dramatically alter the surface of the protein implicated in binding ligand.

CONCLUSIONS

Our observations provide the first atomic resolution view of conformational changes in an integrin domain, and suggest how these changes are linked to a change in integrin adhesiveness. We propose that the Mg2+ form represents the conformation of the domain in the active state and the Mn2+ form the conformation in the inactive state of the integrin.

Pendred's syndrome: a study of patients and relatives

Four families, 29 members, with Pendred's syndrome were studied to clarify hearing loss and hormonal status. The ages ranged from 3 to 50 years. Complete Pendred's syndrome was found in 9 patients. They had bilateral profound hearing loss with residual hearing at low frequencies. Goiter was diagnosed at the age of 1 to 14 years with a positive perchlorate discharge test. Twelve of the patients' relatives showed partial Pendred's syndrome. Mild sensorineural hearing losses occurred in the low- and medium-range frequencies with normal perchlorate discharge test results in 6 cases. The other 6 had a slight drop in the perchlorate discharge test results with normal hearing. Five subjects were normal and 3 had normal hormonal and normal perchlorate discharge test results, but were not tested audiologically. This paper shows that patients with Pendred's syndrome may have goiter at birth or develop it between 8 and 14 years, that their deafness is bilateral and profound, and that their perchlorate discharge tests are positive. Relatives of Pendred's syndrome patients showed mild low-frequency sensorineural hearing loss without goiter and normal perchlorate discharge test results in half the cases, and a slight drop in the perchlorate discharge test results with normal hearing and without goiter in the other half. A correlation between these findings and genetic studies needs further investigation.

Intercellular adhesion molecule-2 (CD102) binds to the leukocyte integrin CD11b/CD18 through the A domain

The interactions between the leukocyte-specific beta 2-integrins cluster of differentiation (CD) Ag CD11/CD18 and their ligands, the intercellular adhesion molecules (ICAMs), play important roles in many adhesion-dependent leukocyte functions. ICAM-1 is known to be a ligand for both CD11a/CD18 and CD11b/CD18. ICAM-2, whose two extracellular Ig domains show the highest homology to the two NH2-terminal domains of ICAM-1, has been previously shown to be a ligand for CD11a/CD18. We recently found that a 22-amino acid CD11a/CD18-binding peptide, P1, derived from the first domain of ICAM-2, also binds to purified CD11b/CD18. In the present study, we demonstrate that the ICAM-2 protein interacts with CD11b/CD18, and the binding is through the CD11b A domain.

Intercellular adhesion molecule-2 (CD102) binds to the leukocyte integrin CD11b/CD18 through the A domain

The interactions between the leukocyte-specific beta 2-integrins cluster of differentiation (CD) Ag CD11/CD18 and their ligands, the intercellular adhesion molecules (ICAMs), play important roles in many adhesion-dependent leukocyte functions. ICAM-1 is known to be a ligand for both CD11a/CD18 and CD11b/CD18. ICAM-2, whose two extracellular Ig domains show the highest homology to the two NH2-terminal domains of ICAM-1, has been previously shown to be a ligand for CD11a/CD18. We recently found that a 22-amino acid CD11a/CD18-binding peptide, P1, derived from the first domain of ICAM-2, also binds to purified CD11b/CD18. In the present study, we demonstrate that the ICAM-2 protein interacts with CD11b/CD18, and the binding is through the CD11b A domain.

Preventing the infiltration of leukocytes by monoclonal antibody blocks the development of progressive ischemia in rat burns

Tissue loss as a consequence of thermal trauma occurs in two stages. There is immediate necrosis in tissues directly killed by the thermal energy, followed by a delayed secondary necrosis in neighboring tissues. The infiltration of neutrophils into traumatized tissues is a hallmark of the inflammatory response. Neutrophils have the machinery to kill invading microorganisms, but these same weapons have the capacity to destroy the host's viable tissues as well. Leukocyte infiltration requires their adherence to the vascular endothelial cell surface. Masking these adhesion sites on neutrophils will block the adhesion of neutrophils to the endothelium. A monoclonal antibody (mAb) was developed to guinea pig leukocyte adhesion sites CD11b/ CD18, and this mAb cross-reacts with rat leukocytes, blocking their adherence. Rats received a "comb burn" composed of four rectangular full-thickness burns placed in a row and separated by three areas left unburned. The four individual burns convert into a single large wound because the blood flow to the interspaces was terminated, blood vessels were occluded, and leukocytes were present in the extravascular space. The systemic administration of the mAb (50 to 150 microliters) immediately following a comb burn promoted the survival of the interspace, demonstrated by the prevention of loss of blood flow by laser Doppler monitoring, maintained patent vessels by latex vascular casts, blocked extravascular migration of neutrophils histologically at 2 hours, and limited the tissue loss to the original four burns.

Inhibition of proteinase 3 by ANCA and its correlation with disease activity in Wegener's granulomatosis

Detection of circulating antineutrophil cytoplasmic antibodies (ANCA) to the neutrophil serine proteinase, proteinase 3 (PR3), has proven valuable for the diagnosis of Wegener's granulomatosis (WG). However, the importance of these autoantibodies in the pathogenesis of WG remains unknown. It was recently reported that anti-PR3 autoantibodies (PR3-ANCA) from some patients with WG inhibit the proteolytic activity of PR3 and interfere with the inactivation of PR3 by the physiologic inhibitor, alpha 1-proteinase inhibitor (alpha 1-PI). We have studied the effect of PR3-ANCA on the enzymatic activity of PR3 and its correlation with disease activity in patients with WG. We purified IgG from 21 PR3-ANCA positive sera obtained from 17 patients with WG, and determined its effect on the esterolytic and proteolytic activity of purified human PR3 using Boc-Ala-O-Nitrophenyl ester and fluoresceinated-elastin as enzyme substrates. Controls included seven sera containing anti-MPO autoantibodies (MPO-ANCA) from patients with systemic vasculitis and seven ANCA-negative sera obtained from healthy individuals. We found that PR3-ANCA from 9 of the 17 patients significantly inhibited the activity of PR3. There was no correlation between the titers of PR3-ANCA and their inhibitory activity. For one extensively characterized autoantibody, the inhibition reached 70 to 95% at 20-fold molar excess of IgG to enzyme, with an apparent Kiapp of 56.5 microM. This inhibition was non-competitive in nature, and was additive to that produced by alpha 1-PI. A review of the clinical histories of the patients revealed a strong association between active WG and inhibitory autoantibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Direct interaction of filamin (ABP-280) with the beta 2-integrin subunit CD18

beta 2-Integrins mediate leukocyte extravasation into inflamed tissues, phagocytosis, and target cell killing, functions that require an intact actin cytoskeleton. Previous studies have focused on elucidating interactions of the cytoplasmic tails of integrins with the cytoskeleton at focal contacts in stationary cells. As integrins are also located at other types of cell-substratum junctions, such as the leading edge of migrating cells, additional cytosolic proteins abundant at these sites may also interact with integrins. In this study, we have identified the actin-binding protein, filamin (ABP-280), as a major cytoskeletal protein that binds to the cytoplasmic tail of the beta 2-integrin subunit CD18. Filamin bound to cytoplasmic CD18 directly and specifically, co-immunoprecipitated with beta 2-integrins in detergent cell lysate and co-immunolocalized with cross-linked beta 2-integrins in intact cells. The filamin binding site in CD18 was localized to the N-terminal (amino acids (aa) 724 to 747) but not to the C-terminal (aa 743 to 769) half of cytoplasmic CD18. Filamin did not bind to the major alpha-actinin binding site (aa 733 to 742), however, suggesting that these two cytoskeletal proteins bind to distinct but overlapping sites. Given the conservation of the filamin binding region among beta-integrin subunits, these findings suggest the presence of similar associations between filamin and other integrins. These associations may be important in the spreading and extension of lamellipodia at the leading edge during cell movement and, if interrupted, may contribute to the dramatic decrease in cell locomotion observed in genetic deletions involving filamin or integrins.

Direct interaction of filamin (ABP-280) with the beta 2-integrin subunit CD18

beta 2-Integrins mediate leukocyte extravasation into inflamed tissues, phagocytosis, and target cell killing, functions that require an intact actin cytoskeleton. Previous studies have focused on elucidating interactions of the cytoplasmic tails of integrins with the cytoskeleton at focal contacts in stationary cells. As integrins are also located at other types of cell-substratum junctions, such as the leading edge of migrating cells, additional cytosolic proteins abundant at these sites may also interact with integrins. In this study, we have identified the actin-binding protein, filamin (ABP-280), as a major cytoskeletal protein that binds to the cytoplasmic tail of the beta 2-integrin subunit CD18. Filamin bound to cytoplasmic CD18 directly and specifically, co-immunoprecipitated with beta 2-integrins in detergent cell lysate and co-immunolocalized with cross-linked beta 2-integrins in intact cells. The filamin binding site in CD18 was localized to the N-terminal (amino acids (aa) 724 to 747) but not to the C-terminal (aa 743 to 769) half of cytoplasmic CD18. Filamin did not bind to the major alpha-actinin binding site (aa 733 to 742), however, suggesting that these two cytoskeletal proteins bind to distinct but overlapping sites. Given the conservation of the filamin binding region among beta-integrin subunits, these findings suggest the presence of similar associations between filamin and other integrins. These associations may be important in the spreading and extension of lamellipodia at the leading edge during cell movement and, if interrupted, may contribute to the dramatic decrease in cell locomotion observed in genetic deletions involving filamin or integrins.

Crystal structure of the A domain from the alpha subunit of integrin CR3 (CD11b/CD18)

We have determined the high resolution crystal structure of the A domain from the alpha chain of integrin CR3. The domain adopts a classic alpha/beta "Rossmann" fold and contains an unusual Mg2+ coordination site at its surface. One of the coordinating ligands is the glutamate side chain from another A domain molecule. We suggest that this site represents a general metal ion-dependent adhesion site (MIDAS) for binding protein ligands. We further propose that the beta subunits of integrins contain a MIDAS motif within a modified A domain. Our crystal structure will allow reliable models to be built for other members of the A domain superfamily and should facilitate development of novel adhesion modulatory drugs.

The A-domain of beta 2 integrin CR3 (CD11b/CD18) is a receptor for the hookworm-derived neutrophil adhesion inhibitor NIF

The A-domain is a approximately 200-amino acid peptide present within structurally diverse proadhesive proteins including seven integrins. A recombinant form of the A-domain of beta 2 integrins CR3 and LFA-1 has been recently shown to bind divalent cations and to contain binding sites for protein ligands that play essential roles in leukocyte trafficking to inflammatory sites, phagocytosis and target cell killing. In this report we demonstrate that the neutrophil adhesion inhibitor, NIF produced by the hookworm Ancyclostoma caninium is a selective CD11b A-domain binding protein. NIF bound directly, specifically and with high affinity (Kd of approximately 1 nM) to recombinant CD11b A-domain (r11bA). The binding reaction was characterized by rapid association and very slow dissociation, and was blocked by an anti-r11bA monoclonal antibody. No binding was observed to rCD11aA. The NIF-r11bA interaction required divalent cations, and was absent when the mutant r11bA D140GS/AGA (that lacks divalent cation binding capacity) was used. The NIF binding site in r11bA was mapped to four short peptides, one of which being an iC3b binding site. The interaction of NIF with CR3 in intact cells followed similar binding kinetics to those with r11bA, and occurred with similar affinity in resting and activated human neutrophils, suggesting that the NIF epitope is activation independent. Binding of NIF to CR3 blocked its ability to bind to its ligands iC3b, fibrinogen, and CD54, and inhibited the ability of human neutrophils to ingest serum opsonized particles. NIF thus represents the first example of a disintegrin that targets the integrin A-domain, and is likely to be used by the hookworm to evade the host's inflammatory response. The unique structure of NIF, which lacks a disintegrin motif, emphasizes basic structural differences in antagonists targeting A+ and A- integrins, that should be valuable in drug design efforts aimed at generating novel therapeutics. Identification of the region in NIF mediating A-domain binding should also be useful in this regard, and may, as in the case of disintegrins, unravel a new structural motif with cellular counterparts mediating important physiologic functions.

Identification of the complement iC3b binding site in the beta 2 integrin CR3 (CD11b/CD18)

The divalent cation-dependent interaction of the beta 2 integrin CR3 (CD11b/CD18) with the major complement opsonic C3 fragment iC3b is an important component of the central role of CR3 in inflammation and immune clearance. In this investigation we have identified the iC3b binding site in CR3. A recombinant fragment representing the CR3 A-domain, a 200-amino acid region in the ectodomain of the CD11b subunit, bound to iC3b directly and in a divalent cation-dependent manner. The iC3b binding site was further localized to a short linear peptide that also bound iC3b directly and inhibited iC3b binding to the A-domain as well as to CR3 expressed by human neutrophils. These data establish a major recognition function for the integrin A-domain and have important implications for development of novel antiinflammatory therapeutics.

The human beta 2 integrin CD18 promoter consists of two inverted Ets cis elements

To define the minimal promoter responsible for expression of CD18 in myeloid and lymphoid cells, we generated 5' and 3' deletion constructs of a segment extending 785 bp upstream and 19 bp downstream of a major transcription start site and determined their effects on driving expression of the luciferase reporter gene in transfected hematopoietic cell lines. A region extending from nucleotides (nt) -302 to +19 was sufficient for cell-restricted and phorbol ester-inducible expression. DNase I footprinting of this region revealed two adjacent protected segments extending from nt -81 to -68 (box A) and -55 to -41 (box B). When a construct of 47 nt in length containing box A and box B and lacking other 3' or 5' elements was cloned into a promoterless vector, it conferred tissue-specific and phorbol ester-inducible expression. Gel retardation revealed that the protein components of two major protein-DNA complexes that form on both box A and box B and are required for transcriptional activation are members of the Ets oncoprotein family; one is related to the GA-binding protein (GABP), and the other is related to PU.1/Spi-1. The minimal CD18 promoter, lacking TATA, CAAT, and initiator elements and consisting primarily of Ets repeats, may exemplify an emerging class of promoters with which the concerted binding of Ets factors is necessary and sufficient to mediate transcriptional activation through direct recruitment of the basal transcription machinery.

Prevalence of abnormal thyroid function tests in connective tissue disease

The prevalence of thyroid function tests' abnormalities in 170 patients with various connective tissue diseases (CTD) was examined and compared to a group of 100 age- and sex-matched controls. The overall prevalence of diagnosed thyroid disease was 3.5%. Categorizing the patients into 5 "functional groups" by the concurrent thyroid function test/results showed normal thyroid function tests in 14%, isolated elevated TSH levels with normal T4 and T3 levels in 4% and findings consistent with the laboratory diagnosis of primary hypothyroidism in 3%. The "euthyroid sick syndrome" was evidenced in 54% and elevated T4 levels and/or increased or normal T3 values with normal TSH in 25%. Antimicrosomal antibodies were noted in 12 patients (7%), with the highest incidence in systemic lupus erythromatosus patients (10%). patients with mixed connective tissue disease had significantly (p < 0.0005) higher frequency of hypothyroidism, whereas patients with systemic vasculities had higher frequency of hyperthyroxinemia. In conclusion, CTD patients frequently have abnormal results of one or more of thyroid function tests. Hypothyroidism and hyperthyroidism should be considered when evaluating symptoms and signs in CTD and a significant subset of CTD patients appears to be predisposed to the development of hyperthyroidism.

Molecular cloning of a novel human hsp70 from a B cell line and its assignment to chromosome 5

A 2391-bp cDNA encoding a novel human hsp70, named hsp70 RY, is described. It was cloned from a cDNA library constructed using mRNA derived from an established EBV-transformed B cell line from a patient with leukocyte adhesion molecule deficiency. hsp70 RY is 701 amino acids long, has the characteristic N-terminal ATP-binding domain and the C-terminal peptide binding domain, and contains four potential N-glycosylation sites. Northern blotting revealed a single mRNA species of 3.0 kb in total RNA prepared from the patient's EBV cell line. In situ hybridization localized the single copy hsp70 RY gene to the long arm of chromosome 5 at 5 q31.1-5 q31.2.

Molecular cloning of a novel human hsp70 from a B cell line and its assignment to chromosome 5

A 2391-bp cDNA encoding a novel human hsp70, named hsp70 RY, is described. It was cloned from a cDNA library constructed using mRNA derived from an established EBV-transformed B cell line from a patient with leukocyte adhesion molecule deficiency. hsp70 RY is 701 amino acids long, has the characteristic N-terminal ATP-binding domain and the C-terminal peptide binding domain, and contains four potential N-glycosylation sites. Northern blotting revealed a single mRNA species of 3.0 kb in total RNA prepared from the patient's EBV cell line. In situ hybridization localized the single copy hsp70 RY gene to the long arm of chromosome 5 at 5 q31.1-5 q31.2.