Mutagenesis of the conserved residue Glu259 of Gsalpha demonstrates the importance of interactions between switches 2 and 3 for activation

We previously reported that substitution of Arg258 within the switch 3 region of Gsalpha impaired activation and increased basal GDP release due to loss of an interaction between the helical and GTPase domains (Warner, D. R., Weng, G., Yu, S., Matalon, R., and Weinstein, L. S. (1998) J Biol. Chem. 273, 23976-23983). The adjacent residue (Glu259) is strictly conserved in G protein alpha-subunits and is predicted to be important in activation. To determine the importance of Glu259, this residue was mutated to Ala (Gsalpha-E259A), Gln (Gsalpha-E259Q), Asp (Gsalpha-E259D), or Val (Gsalpha-E259V), and the properties of in vitro translation products were examined. The Gsalpha-E259V was studied because this mutation was identified in a patient with Albright hereditary osteodystrophy. S49 cyc reconstitution assays demonstrated that Gsalpha-E259D stimulated adenylyl cyclase normally in the presence of GTPgammaS but was less efficient with isoproterenol or AlF4-. The other mutants had more severely impaired effector activation, particularly in response to AlF4-. In trypsin protection assays, GTPgammaS was a more effective activator than AlF4- for all mutants, with Gsalpha-E259D being the least severely impaired. For Gsalpha-E259D, the AlF4--induced activation defect was more pronounced at low Mg2+ concentrations. Gsalpha-E259D and Gsalpha-E259A purified from Escherichia coli had normal rates of GDP release (as assessed by the rate GTPgammaS binding). However, for both mutants, the ability of AlF4- to decrease the rate of GTPgammaS binding was impaired, suggesting that they bound AlF4- more poorly. GTPgammaS bound to purified Gsalpha-E259D irreversibly in the presence of 1 mM free Mg2+, but dissociated readily at micromolar concentrations. Sucrose density gradient analysis of in vitro translates demonstrated that all mutants except Gsalpha-E259V bind to beta gamma at 0 degreesC and were stable at higher temperatures. In the active conformation Glu259 interacts with conserved residues in the switch 2 region that are important in maintaining both the active state and AlF4- in the guanine nucleotide binding pocket. Although both Gsalpha Arg258 and Glu259 are critical for activation, the mechanisms by which these residues affect Gsalpha protein activation are distinct.     

Nonimmune hydrops fetalis: fetal and neonatal outcome during 1983-1992

Prognostic factors for survival of 62 fetuses and neonates with nonimmune hydrops fetalis (NIHF) were studied retrospectively. Twenty-eight infants survived >/=28 days which is 45% for all fetuses and newborns diagnosed with NIHF and 61% for liveborns with unresolved NIHF. Univariate analysis identified that mortality was associated with the presence of >/=2 serous cavity effusions and a need for chest compressions at birth. Multivariate logistic regression analysis confirmed that the presence of >/=2 serous cavity effusions was significantly associated with mortality from NIHF <28 days after birth [OR = 48.2 (CI 3.6, 662.9) (p < 0.004)]. We conclude that, compared to published cases from the 1970s and early 1980s, survival of liveborns with NIHF seems improved. The decrease in stillbirths is more notable. The severity of hydrops at birth is the key determinant for survival.     

Intravascular lymphomatosis: a case presenting with encephalomyelitis and reactive haemophagocytic syndrome diagnosed by renal biopsy

OBJECTIVE: To determine the frequency of characteristics associated with unprotected heterosexual intercourse in HIV infected adults in an urban area. DESIGN: Retrospective comparison of sexual risk transmission behaviour between HIV infected men and women from a drug treatment site and between women from the drug site and HIV infected women from an urban medical centre. METHODS: HIV infected women and men were asked questions on sexual behaviour for a 1 year period before enrollment. The outcome variable was heterosexual risk behaviour (HRB) defined as having vaginal sex at least once in the previous year and not always using condoms. RESULTS: 73% of the drug clinic females, 72% of the drug clinic males, and 42% of the medical centre female engaged in HRB. Using logistic regression analysis, women and men in drug treatment engaged in similar rates of HRB; however, women in drug treatment were four times (95% CI = 2.0-8.3) more likely to engage in HRB risk behaviour than women from the medical centre. CONCLUSION: The data suggest that a surprisingly large portion of HIV infected patients under treatment engaged in HRB, especially former drug users. Without specifically targeted interventions, the heterosexual spread of HIV in urban areas will continue to be a serious problem.