Berardinelli-Seip congenital lipodystrophy 2 regulates adipocyte lipolysis,browning, and energy balance in adult animals

Mutations in BSCL2/SEIPIN cause Berardinelli-Seip congenital lipodystrophy type 2 (BSCL2), but the mechanisms whereby Bscl2 regulates adipose tissue function are unclear. Here, we generated adipose tissue (mature) Bscl2 knockout (Ad-mKO) mice, in which Bscl2 was specifically ablated in adipocytes of adult animals, to investigate the impact of acquired Bscl2 deletion on adipose tissue function and energy balance. Ad-mKO mice displayed reduced adiposity and were protected against high fat diet-induced obesity, but not insulin resistance or hepatic steatosis. Gene expression profiling and biochemical assays revealed increased lipolysis and fatty acid oxidation in white adipose tissue (WAT) and brown adipose tissue , as well as browning of WAT, owing to induction of cAMP/protein kinase A signaling upon Bscl2 deletion. Interestingly, Bscl2 deletion reduced food intake and downregulated adipose β3-adrenergic receptor (ADRB3) expression. Impaired ADRB3 signaling partially offsets upregulated browning-induced energy expenditure and thermogenesis in Ad-mKO mice housed at ambient temperature. However, this counter-regulatory response was abrogated under thermoneutral conditions, resulting in even greater body mass loss in Ad-mKO mice. These findings suggest that Bscl2 regulates adipocyte lipolysis and β-adrenergic signaling to produce complex effects on adipose tissues and whole-body energy balance.     

Two serine residues control sequential steps during catalysis of the yeast copper ATPase through different mechanisms that involve kinase-mediated phosphorylations

Ccc2, the yeast copper-transporting ATPase, pumps copper from the cytosol to the Golgi lumen. During its catalytic cycle, Ccc2 undergoes auto-phosphorylation on Asp(627) and uses the energy gained to transport copper across the cell membrane. We previously demonstrated that cAMP-dependent protein kinase (PKA) controls the energy interconversion (Cu)E～P → E-P + Cu when Ser(258) is phosphorylated. We now demonstrate that Ser(258) is essential in vivo for copper homeostasis in extremely low copper and iron concentrations. The S258A mutation abrogates all PKA-mediated phosphorylations of Ccc2, whereas the S971A mutation leads to a 100% increase in its global regulatory phosphorylation. With S258A, the first-order rate constant of catalytic phosphorylation by ATP decreases from 0.057 to 0.030 s(-1), with an 8-fold decrease in the burst of initial phosphorylation. With the S971A mutant, the rate constant decreases to 0.007 s(-1). PKAi(5-24) decreases the amount of the aspartylphosphate intermediate (EP) in Ccc2 wt by 50% within 1 min, but not in S258A, S971A, or S258A/S971A. The increase of the initial burst and the extremely slow phosphorylation when the "phosphomimetic" mutant S258D was assayed (k = 0.0036 s(-1)), indicate that electrostatic and conformational (non-electrostatic) mechanisms are involved in the regulatory role of Ser(258). Accumulation of an ADP-insensitive form in S971A demonstrates that Ser(971) is required to accelerate the hydrolysis of the E-P form during turnover. We propose that Ser(258) and Ser(971) are under long-range intramolecular, reciprocal and concerted control, in a sequential process that is crucial for catalysis and copper transport in the yeast copper ATPase.     

Neurologic Manifestations Associated with an Outbreak of Typhoid Fever, Malawi - Mozambique, 2009: An Epidemiologic Investigation

Background

The bacterium Salmonella enterica serovar Typhi causes typhoid fever, which is typically associated with fever and abdominal pain. An outbreak of typhoid fever in Malawi-Mozambique in 2009 was notable for a high proportion of neurologic illness.

Objective

Describe neurologic features complicating typhoid fever during an outbreak in Malawi-Mozambique

Methods

Persons meeting a clinical case definition were identified through surveillance, with laboratory confirmation of typhoid by antibody testing or blood/stool culture. We gathered demographic and clinical information, examined patients, and evaluated a subset of patients 11 months after onset. A sample of persons with and without neurologic signs was tested for vitamin B6 and B12 levels and urinary thiocyanate.

Results

Between March – November 2009, 303 cases of typhoid fever were identified. Forty (13%) persons had objective neurologic findings, including 14 confirmed by culture/serology; 27 (68%) were hospitalized, and 5 (13%) died. Seventeen (43%) had a constellation of upper motor neuron findings, including hyperreflexia, spasticity, or sustained ankle clonus. Other neurologic features included ataxia (22, 55%), parkinsonism (8, 20%), and tremors (4, 10%). Brain MRI of 3 (ages 5, 7, and 18 years) demonstrated cerebral atrophy but no other abnormalities. Of 13 patients re-evaluated 11 months later, 11 recovered completely, and 2 had persistent hyperreflexia and ataxia. Vitamin B6 levels were markedly low in typhoid fever patients both with and without neurologic signs.

Conclusions

Neurologic signs may complicate typhoid fever, and the diagnosis should be considered in persons with acute febrile neurologic illness in endemic areas.     

Population-based incidence of typhoid fever in an urban informal settlement and a rural area in Kenya: implications for typhoid vaccine use in Africa

Background

High rates of typhoid fever in children in urban settings in Asia have led to focus on childhood immunization in Asian cities, but not in Africa, where data, mostly from rural areas, have shown low disease incidence. We set out to compare incidence of typhoid fever in a densely populated urban slum and a rural community in Kenya, hypothesizing higher rates in the urban area, given crowding and suboptimal access to safe water, sanitation and hygiene.

Methods

During 2007-9, we conducted population-based surveillance in Kibera, an urban informal settlement in Nairobi, and in Lwak, a rural area in western Kenya. Participants had free access to study clinics; field workers visited their homes biweekly to collect information about acute illnesses. In clinic, blood cultures were processed from patients with fever or pneumonia. Crude and adjusted incidence rates were calculated.

Results

In the urban site, the overall crude incidence of Salmonella enterica serovar Typhi (S. Typhi) bacteremia was 247 cases per 100,000 person-years of observation (pyo) with highest rates in children 5–9 years old (596 per 100,000 pyo) and 2–4 years old (521 per 100,000 pyo). Crude overall incidence in Lwak was 29 cases per 100,000 pyo with low rates in children 2–4 and 5–9 years old (28 and 18 cases per 100,000 pyo, respectively). Adjusted incidence rates were highest in 2–4 year old urban children (2,243 per 100,000 pyo) which were >15-fold higher than rates in the rural site for the same age group. Nearly 75% of S. Typhi isolates were multi-drug resistant.

Conclusions

This systematic urban slum and rural comparison showed dramatically higher typhoid incidence among urban children <10 years old with rates similar to those from Asian urban slums. The findings have potential policy implications for use of typhoid vaccines in increasingly urban Africa.     

CadA, the Cd2+-ATPase from Listeria monocytogenes, can use Cd2+ as co-substrate

CadA is a membrane protein of the P-type ATPase family which is the major determinant of the resistance to Cd2+ in Listeria monocytogenes. During its catalytic cycle, CadA undergoes auto-phosphorylation from ATP at Asp398, which allows Cd2+ translocation across the membrane. In the reverse mode, Asp398 is phosphorylated from Pi. From the data obtained so far, the CadA catalytic mechanism is similar to that proposed for the sarcoplasmic reticulum Ca2+-ATPase, the model of the P-type ATPase family. We show here that CadA is sensitive to two different ranges of Cd2+ concentration. The 0.1-10 microM range of added CdCl2 corresponds to Cd2+ binding at the transport site of unphosphorylated CadA which induces the reaction of the enzyme with ATP and impairs its reaction with Pi. The 0.1-1 mM range of added CdCl2 could correspond to Cd2+ binding to the transport site accessible from the extracellular medium. In addition, although it is widely accepted that the actual substrate of P-type ATPases is the MgATP complex, we show here that CadA can also perform its cycle in the absence of Mg2+, using CdATP in the place of MgATP at the catalytic site.