Phosphorylation of factor Va and factor VIIIa by activated platelets

Platelet activation leads to the incorporation of 32[PO4(2-)] into bovine coagulation factor Va and recombinant human factor VIII. In the presence of the soluble fraction from thrombin-activated platelets and (gamma-32P) adenosine triphosphate, radioactivity is incorporated exclusively into the M(r) = 94,000 heavy chain (H94) of factor Va and into the M(r) = 210,000 to 90,000 heavy chains as well into the M(r) = 80,000 light chain of factor VIII. Proteolysis of the purified phosphorylated M(r) = 94,000 factor Va heavy chain by activated protein C (APC) gave products of M(r) = 70,000, 24,000, and 20,000. Only the intermediate M(r) = 24,000 fragment contained radioactivity. Because the difference between the M(r) = 24,000 and M(r) = 20,000 fragments is located on the COOH-terminal end of the bovine heavy chain, phosphorylation of H94 must occur within the M(r) = 4,000 peptide derived from the carboxyl-terminal end of H94 (residues 663 through 713). Exposure of the radioactive factor VIII molecule to thrombin ultimately resulted in a nonradioactive light chain and an M(r) = 24,000 radioactive fragment that corresponds to the carboxyl-terminal segment of the A1 domain of factor VIII. Based on the known sequence of human factor VIII, phosphorylation of factor VIII by the platelet kinase probably occurs within the acidic regions 337 through 372 and 1649 through 1689 of the procofactor. These acidic regions are highly homologous to sequences known to be phosphorylated by casein kinase II. Results obtained using purified casein kinase II gave a maximum observed stoichiometry of 0.6 mol of 32[PO4(2-)]/mol of factor Va heavy chain and 0.35 mol of 32[PO4(2-)]/mol of factor VIII. Phosphoamino acid analysis of phosphorylated factor Va by casein kinase II or by the platelet kinase showed only the presence of phosphoserine while phosphoamino acid analysis of phosphorylated factor VIII by casein kinase II showed the presence of phosphothreonine as well as small amounts of phosphoserine. The platelet kinase responsible for the phosphorylation of the two cofactors was found to be inhibited by several synthetic protein kinase inhibitors. Finally, partially phosphorylated factor Va was found to be more sensitive to APC inactivation than its native counterpart. Our findings suggest that phosphorylation of factors Va and VIIIa by a platelet casein kinase II- like kinase may downregulate the activity of the two cofactors.     

Assessing the needs of women and clinicians for the management of menopause in an HMO

Objective: To determine the perceived needs of perimenopausal women regarding the management of menopause and the resource needs of the clinicians who treat them. Setting: A large staff and group network model health maintenance organization (HMO) in New England. Participants: A random sample of 790 perimenopausal women aged 45–60 years who were members of the HMO in 1991, and a random sample of 180 clinicians in internal medicine, family practice, and obstetrics/gynecology practicing in the HMO during 1991. Method: Mailed surveys of women and clinicians were designed to assess possible needs and attitudes that could lead to the improvement of care for menopausal women. The chi-square test was used to determine differences in perceived needs and satisfaction levels among women with differences in self-reported menopausal status. The Kruskal-Wallis one-way analysis of variance and the Mann-Whitney U test were used in the clinician survey to test for differences among specialties and between genders. Results: The key findings include that: 1) most (81%) of the women wanted to see a woman clinician, 2) many (50%) were interested in a menopause support group, 3) 30% reported that their care for menopause had been fair to poor, 4) only 55% of the primary care specialists (including internal medicine and family practice) reported high confidence in their abilities to treat menopause, compared with 68% of the obstetric/gynecology clinicians, and 5) 56% of the clinicians surveyed said that support from the HMO to their practices for the treatment of menopause was fair to poor. Conclusions: There is an opportunity for better care for perimenopausal women as reported by two sources, HMO clinicians and members. To provide this care, clinicians may need explicit guidelines as well as administrative supports such as educational materials and specialty access. Since the capability for menopausal care from clinicians in obstetrics/gynecology is perceived to be higher than that from primary care clinicians, an opportunity for cross-specialty collaboration and training may exist.     

Engraftment of dogs with Ia-positive marrow cells isolated by avidin- biotin immunoadsorption

Previous work has shown failure of engraftment in lethally irradiated dogs when autologous marrow was depleted of Ia-positive cells with an anti-Ia antibody and complement before infusion. In the current study, we have utilized an avidin-biotin immunoadsorption procedure to obtain a population of highly enriched Ia-positive cells for autologous bone marrow transplantation in dogs given lethal irradiation. Dog marrow cells (2.4 to 7.0 X 10(9) cells) that contained 8.6% to 19.9% Ia- positive cells were treated successively with monoclonal antibody 7.2, which reacts with a framework determinant of Ia-antigen, and biotin- conjugated goat antimouse immunoglobulin. These treated cells were passed over a column of avidin-Biogel (polyacrylamide) and the adherent cells removed by mechanical agitation. Seven lethally irradiated dogs were transplanted with 5.9 to 33.4 X 10(6) recovered adherent cells per kilogram of which 69.0% to 88.0% were Ia-positive. All dogs had hematologic recovery; six are alive and well with durable engraftment and one died on day 15 posttransplant. They are immunologically normal as determined by lymph node and bone marrow biopsies, lymphocyte function, and immunophenotyping of peripheral blood and bone marrow cells. These data provide further evidence that canine hematopoietic stem cells express Ia-like antigens and that these cells are capable of complete hematopoietic and immunologic reconstitution in an autologous model.     

Enthalpy of hydrogen bond formation in a protein-ligand binding reaction.

Parallel measurements of the thermodynamics(free-energy, enthalpy, entropy and heat-capacity changes) of ligand binding toFK506 binding protein (FKBP-12) in H2O and D2O have been performed in an effortto probe the energetic contributions of single protein-ligand hydrogen bondsformed in the binding reactions. Changing tyrosine-82 to phenylalanine inFKBP-12 abolishes protein-ligand hydrogen bond interactions in the FKBP-12complexes with tacrolimus or rapamycin and leads to a large apparent enthalpicstabilization of binding in both H2O and D2O. High-resolution crystallographicanalysis reveals that two water molecules bound to the tyrosine-82 hydroxylgroup in unliganded FKBP-12 are displaced upon formation of the protein-ligandcomplexes. A thermodynamic analysis is presented that suggests that the removalof polar atoms from water contributes a highly unfavorable enthalpy change tothe formation of C=O...HO hydrogen bonds as they occur in the processes ofprotein folding and ligand binding. Despite the less favorable enthalpy change,the entropic advantage of displacing two water molecules upon binding leads to aslightly more favorable free-energy change of binding in the reactions withwild-type FKBP-12.