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K A Sullivan

Publications and source records attributed to K A Sullivan.

At least 55 records · Page 3Linked to original sources
PubMed1988

Genetic deficiency of the alpha subunit of the guanine nucleotide-binding protein Gs as the molecular basis for Albright hereditary osteodystrophy.

Patients who have pseudohypoparathyroidism type I associated with Albright hereditary osteodystrophy commonly have a genetic deficiency of the alpha subunit of the G protein that stimulates adenylyl cyclase (alpha Gs) (ATP pyrophosphate-lyase, EC 4.6.1.1). To discover the molecular mechanism that causes alpha Gs deficiency in these patients, we examined eight kindreds with one or more members affected with Albright hereditary osteodystrophy or pseudohypoparathyroidism and alpha Gs deficiency. In these families, alpha Gs deficiency and the Albright hereditary osteodystrophy phenotype were transmitted together in a dominant inheritance pattern. Using a cDNA hybridization probe for alpha Gs, restriction analysis with several endonucleases showed no abnormalities of restriction fragments or gene dosage. RNA blot and dot blot analysis of total RNA from cultured fibroblasts obtained from the patients revealed approximately equal to 50% reduced mRNA levels for alpha Gs in affected members of six of the pedigrees but normal levels in affected members of the two other pedigrees, compared to mRNA levels in fibroblasts from unaffected individuals. By contrast, mRNA levels encoding the alpha subunit of the G protein that inhibits adenylyl cyclase were not altered. Our findings suggest that several molecular mechanisms produce alpha Gs deficiency in patients with pseudohypoparathyroidism type Ia and that major gene rearrangements or deletions are not a common cause for alpha Gs deficiency in pseudohypoparathyroidism type I.

Cell Membrane↗
PubMed1988

Mutations probe structure and function of G-protein alpha chains.

The molecular genetic approach has just begun to provide hints of answers to some of the questions posed at the outset of this paper. We have some idea of which portions of the alpha chain of Gs interact with receptors and effectors, and we guess that the same is true of corresponding regions of other alpha chains. We have a tantalizing hint that points to a key region of alpha s that is necessary for the conformational change induced by binding GTP, and the vague outline of a hypothesis regarding the mechanism by which receptors release GDP from its binding site on the alpha chain. The alpha chain region (domain) that interacts with beta gamma remains unknown. The tenuous quality of all these hints and hypotheses is obvious, and at least in the short term, frustrating. Even the present level of our understanding, however, is impressive in comparison with what was known of G-protein function only 5 years ago. Now we can pose much more precise questions and hope that a combination of the molecular genetic approach with biophysical probes of structure will provide satisfying answers.

Animals↗
PubMed1987

Chromosomal assignment of the murine Gi alpha and Gs alpha genes. Implications for the obese mouse.

The G protein family of transmembrane signaling molecules includes Gs and Gi, the stimulatory and inhibitory regulators of adenylate cyclase. These and other characterized G proteins are comprised of beta, gamma, and alpha chains, the latter being the most variable among the proteins and thus serving to distinguish them. Previous results (Begin-Heick, N. (1985) J. Biol. Chem. 260, 6187-6193) suggested that the autosomal recessive mouse mutation obese (ob), which results in an abnormal response of adipose tissue to lipolytic hormones, is due to a defect in the gene coding for the alpha chain of Gi. In order to test this hypothesis we used a cloned cDNA probe representing murine Gi alpha mRNA in conjunction with a panel of Chinese hamster-mouse somatic cell hybrids segregating mouse chromosomes to map the Gi alpha gene in the mouse. In addition, we used a cDNA probe representing the murine Gs alpha gene to a specific mouse chromosome. Our results indicate that the Gi alpha locus maps to mouse chromosome 9, while Gs alpha is localized to region 2E1-2H3 of mouse chromosome 2. Localization of the Gi alpha gene to chromosome 9 excludes this gene as a site of the ob mutation, since the ob locus maps to chromosome 6. Furthermore, our findings indicate that certain members of the murine G protein alpha gene family have dispersed to different chromosomes since diverging from a common ancestral gene.

Animals↗
PubMed1986

Inhibitory and stimulatory G proteins of adenylate cyclase: cDNA and amino acid sequences of the alpha chains.

The G protein family of signal transducers includes five heterotrimers, which are most clearly distinguished by their different alpha chains. The family includes Gs and Gi, the stimulatory and inhibitory GTP-binding regulators of adenylate cyclase; Go, a protein of unknown function abundant in brain; and transducin 1 and transducin 2, proteins involved in retinal phototransduction. Using a bovine alpha t1 cDNA as a hybridization probe, we have isolated mouse cDNAs that encode alpha chains of two G proteins. One encodes a polypeptide of 377 amino acids (Mr 43,856), identified as alpha s because it specifically fails to hybridize with any transcript in an alpha s-deficient S49 mouse lymphoma mutant, cyc-; the other encodes a polypeptide of 355 amino acids (Mr 40,482), presumed to be alpha i. These alpha chains and those of the retinal transducins exhibit impressive sequence homology. Of the four, alpha t1 and alpha t2 are most alike (81% identical amino acid residues), whereas the presumptive alpha i is more similar than alpha s to alpha t1 (63% vs. 38% identical residues). Sequence homologies with p21ras and elongation factor Tu identify regions of the alpha chains that form the site for GTP binding and hydrolysis. Further comparison of the alpha-chain sequences suggests additional regions that may contribute to interactions with beta gamma subunits and the receptor and effector components of different signal transduction systems.

Adenosine Diphosphate Ribose↗
PubMed1986

Mammalian G proteins: models for ras proteins in transmembrane signalling?

How do the p21v-ras proteins and their normal cellular counterparts regulate cell function? What is the molecular basis of action of these proteins? Biochemical, structural and functional similarities between the ras proteins and the vertebrate G proteins offer clues that may help to answer such questions. The G proteins couple a wide array of extracellular signals to regulation of a number of enzyme effectors, including adenylate cyclase, retinal cGMP phosphodiesterase and phospholipase-C. The RAS1 and RAS2 proteins of yeast regulate adenylate cyclase, whereas their close mammalian homologues, the p21ras proteins, do not. Both the ras and the G proteins are located at the cytoplasmic face of the plasma membrane and bind and hydrolyse GTP. Patchy amino acid sequence homologies between the two groups of proteins suggest a common evolutionary origin and common structural features, particularly in the GTP binding domain. In the GTP bound state both proteins are 'on' or activated, and each exhibits an intrinsic GTPase activity that turns off the active state. The analogies between the G and ras proteins suggest that the latter may also couple signal detector and enzymatic effector elements, and suggest strategies for identifying them.

Fungal Proteins↗
PubMed1986

Immunological heterogeneity in human melanoma: immunogenic alloantigen expression in autologous host.

A patient presented with a primary melanoma, Level IV, 2.5 mm thick; 30 excised lymph nodes were all negative for tumor. Four local recurrences followed in the ensuing 17 months. Tumor cells cultured at this time were epithelioid. Autoimmunization was followed by a disease-free interval of 15 months. Postimmunization, the patient's lymphocytes destroyed his melanoma cells in culture and were stimulated in mixed cell culture by his irradiated tumor cells. Cells grown from the relapsing tumor were spindle/dendritic with bizarre morphology and were not attacked by his lymphocytes in culture. Using a C' fixation technique, DR antigen profiles of the patient's B-cells and both tumor cell types showed that the immunizing tumor was positive for DR antigens 3, 5, and 8, none of which were present on his B-cells which had DR 2 and 4. Both B-cells and immunizing tumor cells were positive for DQ antigens. The relapsing tumor cells were positive for DR2 and negative for all other D region antigens tested. The evidence suggests that given a melanoma of heterogeneous cell population, autoimmunization against the predominant immunogenic cell inhibits tumor growth but allows the ascendance of a nonimmunogenic tumor cell type.

Antigens, Neoplasm↗
PubMed1983

Mother-weanling interactions in Norway rats in the presence of a successive litter produced by postpartum mating.

When female Norway rats (Rattus norvegicus) become pregnant at the postpartum estrus they nurse this first litter concurrently with the gestation of a second litter. This second gestation is of variable length (23-31 days in this study) We investigated the behavior of mothers and their older litters around the time the second litter was born. Six female rats gave birth and were mated at the postpartum estrus. Continuous videotaped observation of each female and litter began approximately 3 days before, and continued for 3 days after the birth of the second litter. We found that suckling behavior and nest attendance by the older litter did not necessarily end when the second litter was born. When the gestation length of the second litter was short (23-25 days) older pups continued to spend time in the nest and to nurse along with their newborn siblings. These older pups also spent much time on the nest even in the absence of their mother. When gestation was long (27-31 days) older pups were weaned before the birth of the second litter and spent less time on the nest with the newborns. Stereotyped attacks by the female against her weanling age pups were seen both pre- and postpartum. This maternal aggression did not appear to deter suckling and nest attendance by the weanlings.

Aggression↗
PubMed1982

Evidence for structural similarities in the multiple forms of aortic and cartilage lysyl oxidase and a catalytically quiescent aortic protein.

Lysyl oxidase purified from urea extracts of various connective tissues resolves into multiple catalytically functional species upon chromatography on DEAE-cellulose in 6 M urea. The four enzyme species of bovine aorta retain their original chromatographic behavior on DEAE with time of storage and after purification to homogeneity by gel exclusion chromatography. The peptide maps of each aortic enzyme partially digested by STaphylococcus aureus V8 protease are very similar to each other, as are the peptide maps of complete tryptic digests of each enzyme. Such similarity also exists between the peptide maps of the aortic enzyme and the urea-extractable lysyl oxidase of bovine cartilage, as well as with the peptide maps of a catalytically quiescent protein resolved from the aortic enzyme by gel exclusion chromatography. The substrate activity profiles of the multiple aortic enzyme species are also extremely similar. Although the origin of the enzyme multiplicity remains to be established, there is evident structural and catalytic similarities between the enzyme forms.

Amino Acid Oxidoreductases↗
PubMed1979

Purification and properties of four species of lysyl oxidase from bovine aorta.

Lysyl oxidase of bovine aorta was resolved into four enzymically active species by elution from DEAE-cellulose with a salt gradient in 6m-urea, consistent with purification results obtained with enzyme of other tissues [Stassen (1976) Biochim. Biophys. Acta438, 49-60]. In the present study, each of the four peaks of activity was purified to apparent homogeneity by subsequent chromatography on gel-filtration media in 6m-urea. Each enzyme is eluted as a species with mol.wt. approx. 30000 under these conditions, although lysyl oxidase polymerizes to a series of multimers with molecular weights ranging up to 1000000 in the absence of urea. The apparent subunit molecular weight of each enzyme species determined by electrophoresis in sodium dodecyl sulphate and 8m-urea is approx. 32000-33000. The amino acid compositions of the purified forms of lysyl oxidase are similar to each other, although sufficient differences exist to conclude that each is a unique molecular species. Incorporation of alpha-toluenesulphonyl fluoride into the purification scheme does not alter the resolution of enzyme into four species, suggesting that proteolysis during isolation is not the basis of the heterogeneity. The similar sensitivities of each form of enzyme to chelating agents and to semicarbazide and isoniazid indicate that each requires the participation of a metal ion, presumably Cu(2+), and of a carbonyl compound for enzyme function. The present study describes a method for the purification of multiple species of lysyl oxidase and reveals that significant chemical differences exist between the different enzyme forms.

Amino Acid Oxidoreductases↗
PubMed1979

The Qa-2 antigen on lymphocyte subpopulations. Mixed lymphocyte culture and cell-mediated lympholysis.

Treatments of spleen cells from Qa-2+ strains with Qa-2 antiserum plus complement (C) have revealed that the Qa-2 antigen is present on restricted functional lymphocyte subpopulations. Anti-Qa-2 plus C reduced the mixed lymphocyte culture response and inhibited the generation of cytolytic effector cells. This treatment, however, did not affect cytolytic effector cells once they were generated.

Animals↗
PubMed1978

Qa-2 and Qa-3 antigens on lymphocyte subpopulations. I. Mitogen responsiveness.

The effects of anti-Qa-2 plus C and anti-Qa-3 plus C on mitogen-induced proliferation were studied. Both of these antisera in the presence of C markedly reduced both Con A- and PHA-induced proliferation while having little or no effect on LPS-induced proliferation. LPS, Con A, and PHA cultures and cultures containing media alone, examined at 72 hr, contained high proportions of Qa-2+ and Qa-3+ cells.

Animals↗
PubMed1977

Studies on lysyl oxidase of bovine ligamentum nuchae and bovine aorta.

Lysyl oxidase had been purified to near homogeneity from bovine aorta and bovine ligamentum nuchae employing a modification of methods described by Harris et al., and Stassen and his colleagues. The aortic enzyme gives rise to at least three peaks and the ligament enzyme resolves into at least four peaks upon chromatography on DEAE cellulose. The molecular weight of each peak of both enzymes is approximately 30,000 daltons in sodium dodecyl sulfate. The aortic enzyme aggregates to species with molecular weights varying from approximately 60,000 to 1,000,000 daltons upon dialysis out of urea into phosphate-buffered saline. Temperature studies reveal that lysyl oxidase is stable to temperatures as high as 80 degrees C, although the assay optimum is 52 degrees C. Studies in progress suggest the temperature dependency of assay may reflect conformational changes in the elastin substrate.

Amino Acid Oxidoreductases↗
PubMed1972

Rejection of ascites tumor allografts. II. A pathway for cell-mediated tumor destruction in vitro by peritoneal exudate lymphoid cells.

A pathway for cell-mediated tumor destruction in vitro by immune peritoneal exudate lymphoid cells has been proposed. The union of lymphocytes and tumor cells precedes the formation of an intermediate phase leading to lysis. The initial interaction is only partially temperature dependent. The cytolytic process per se is highly temperature dependent, being negligible at 25 degrees C but proceeding rapidly at 37 degrees C. (51)Cr release from tumor cells is demonstrable within 10 min at 37 degrees C and can be reversibly arrested by cooling. Once initiated, lysis is largely independent of additional interactions and continues at almost full rate for 30 min. The effector cells are not lysed and appear to be free to enter into further effector cycles.

Animals↗