Protein Pathologies: Amyloid guided by glycans

Functional Glycomics (11 November 2010) | doi:10.1038/fg.2010.36

Mutational analysis and tracking of glycosylated isoforms suggest a functional role for glycans in amyloid processing.

 

Amyloid-beta peptides have been closely linked to Alzheimer’s disease, but identifying the mechanism of pathogenicity and even which species is most important in the process, has proved difficult.In addition, it is now common to study amyloid deposition associated with neurons, Amyloid-beta is also deposited in the blood vessels of the brain. By turning their attention to the relevant brain microvascular endothelial cells-BMECs, Taniguchi and colleagues now identify an alternate amyloid-beta precursor and its glycosylation status, as having an unexpected role in the process.

Amyloid precursor protein-APP has three alternative isoforms:APP695 is primarily expressed in neurons, whereas APP751 and APP770 are expressed in several cell types. In addition to the APP695 sequence,APP751 contains the Kunitz-type protease inhibitor-KPI domain, where APP770 includes the KPI domain in tandem with an OX2 domain. Each sequence can be cleaved by Beta-secretase and other enzymes to yield the disease-associated peptides Amyloid beta40 and Amyloid beta 42.

Reporting in the Journal of Biological Chemistry, the authors first describe western blotting and other experiments that indicate that BMECs express more APP than do neurons. Furthermore, neurons express only APP695 as expected whereas BMECs express a substantial amount of APP770. The western blot analysis also revealed a high molecular weight band in the BMEC sample; as previous work has suggested that APP might be glycosylated, the authors used a series of enzymatic treatments and lectin pull down assays to identify N-glycan chains, including high mannose or hybrid glycans and sialylated O-glycans as likely APP modifications, the authors further investigated the OX2 domain, which is unique to this isoform. Mutation of each serine or threonine residue in this region identified Thr353 as a probable point of attachment for an O-glycan but mutation of four additional sites outside this domain guided by previous research was required to completely abrogate O-glycosylation.

These results demonstrated that APP770 is modified by several sugar chains, but what is the role of these carbohydrates? Although several glycoforms could be detected in the cell lysate, the authors detected only a single processed sequence in the cell media. The molecular weight of this processed ‘sAPP’ showed that the polypetide was derived from the high molecular weight APP770 , this origin was explained by a combination of biotinylation experiments.

What Alcohol Actually Does to Your Brain and Body

Lifehacker.com

Alcohol like caffeine, has an enormous reputation but loose understanding in popular culture.

Everyone, it seems, takes their cues on how alcohol affects the mind and body from an eclectic mix of knowledge: personal experience, pop culture, tall tales of long nights, the latest studies to make the health news wires and second hand tips.You might have gathered that alcohol is a depressant, that it’s dehydrating, that you can drink about one drink an hour and stay relatively sober. Some of that is true. But much of it depends on a large number of factors.

Taken from “Buzz: The Science and Lore of Alchol and Caffeine”.

Your body sees alcohol as a poison  or at least as something it doesn’t actually want inside it. To fight back and sober you up, humans have evolved to produce Alcohol Dehydrogenase.

That enzyme gets its shot at your alcohol when it attempts to pass through the stomach lining and when it reaches your liver, primarily.  On contact, it snatches a hydrogen atom off the ethanol molecules in your drink, rendering it into intoxicating acetaldehyde.

Human can then use aldehyde dehydrogenase as a kind of clean up crew, breaking down the aldehyde that’s sometimes considered a cause of hangovers, along with dehydration.

It’s a fight between how much you can drink, versus how fast your enzymes can bust down your indulgences and their by products. But many factors affect certain people’s production of the two alcohol- crushing compounds.

Alcohol Dehydrogenase: more effective in men than in women. Young men, in fact, may have up to 70 to 80 percent greater enzyme activity in the presence of alcohol. But men’s AD effectiveness also drops off with age at a faster rate than in women, such that , by around 55 or 60 , men may find themselves able to handle less alcohol than their female counterparts.

Full stomach:helps break down alcohol, but not because your food “soaks up” the alcohol. When you eat a big mean, your stomach’s pyloric sphincter, a kind of release valve into the small intestine, closes tightly. Your body knows that you’ve got food that should get a good going over in your stomach before it heads straight to the high absorption small intestine, so it keep it there and the AD in your stomach has more time to work on the alcohol.

Drink on an empty stomach and the liquid quickly makes it into the small intestine, where there’s more than 200 square meters of surface area for absorption into your body.

Genetics: Your great-great-grandparents have a say in how buzzed your Friday night gets, for sure, but for roughly on third to half of Asian drinkers, it’s more than a slight variance. Alcohol flush reaction, a flushing of the face when drinking, occurs because the enzyme “clean-up-crew”, AD is mutated by just one amino acid. That changes how effective its molecules are in bonding with and busting up, acetaldehyde. With excess acetaldehyde in their system, those with a flush reaction get red-faced and can experience heart palpitations, dizziness & severe nausea in extreme cases.

Aspirin: Don’t take aspirin before drinking. Aspirin seriously cuts the effectiveness of your bod’s AD enzymes. In one  1990 study, the average blood alcohol levels of those who took two maximum strength aspirin tablets before drinking were an average of 26 percent higher than those who were aspirin free. Other studies have suggested even more impact on your body’s ability to break down alcohol. That also means more acetaldehyde in your system down the line, so you will learn your lesson quickly if you are considering aspirin as a helper.

Absorption and Elimination Is a Curve, Not a Straight Line: Your Blood Alcohol Calculator moves through plateaus, responds differently to drinks higher than 20- 25 percent alcohol by volume and eliminates some alcohol in pure form- which is how police can measure it on your breath.

It Extends Your Life—Kind Of: Alcoholism:Clinical and Experimental Research, researchers followed 1824 people over a total of 20 years, as they aged between 55 and 65. Of those who abstained entirely, 69 percent died. Among those who drank in “moderate” amounts, 41 percent died- which was 23 percent less than the “light” drinkers. Even “heavy drinkers” fared better than abstainers, with just 61 percent passing away during the study period.

Popular theories center on the antioxidants and reservatrol compounds found in wines or on the studies showing alcohol as increasing levels of HDL(“good”) cholesterol.

It Doesn’t “Kill” Brain Cells, but Does Inhibit Them: It’s true that a high concentrations, like the nearly 100% pure alcohol used in sterilizing solutions, alcohol can indeed kill cells and neurons. But given that the blood reaching your brain is only at 0.08% percent alcohol if you are legally intoxicated.

What alcohol can and does do to your brain is affect the way your neurons get their firing triggers from glutamate.It infiltrates the glutamate receptors in your synapses, hurting their ability to send off their normal “fire” messages. Alcohol has this impact all  across your brain- the parts that control muscles, speech, coordination, judgment and so on.

That’s Also Why it, Uh, “Inhibits” Sex: The studies and implications are numerous, to say the least, but if you want a thumbnail understanding of how alcohol, as Shakespeare put it, “provokes the desire, but.. takes away the performance,” it has to do with the firing of nerves , in the brain and elsewhere, that would relax the arteries enough to get both parties moving. It’s a bit more complex than that and drinking in moderation can be a net benefit in some cases, but alcohol, paradoxically, doesn’t help one specific region of your self to “relax”.

Alcohol is Particularly Effective at Inhibiting Memories: N-Methyl-D-aspartic acid or NMDA, the receptor for which alcohol seems particularly  adept at interfering with, studies have shown that while subjects under alcohol’s influence can recall existing memories, events happening during inebriation are regularly hard to remember. It varies with the amount consumed and seems to top out at a serious 0.2% blood alcohol content.

It Makes Other People Seems More “Intentional” :If you’d never been raised to think things through, you’d assume that most actions people took were fairly intentional and possibly pointed at causing you harm.

It’s a Terrible Sleep Aid:Ever heard the term “nightcap?” People have long believed that alcohol helps you get to sleep and that part can be true, for some. Once you’re asleep, though, alcohol’s interaction with your brain can lead to some fitful sleep and no sleep at all, especially if you consumed caffeine anytime close to hitting the pillow. Caffeine, take up to 5 Hours to break down half a dose.

Emory Joins Network

Emory University researchers recently joined the Florida Node Alliance of the National Institute on Drug Abuse's Clinical Trials Network. CTN works to improve substance abuse treatment by linking researchers with care providers. Emory was chosen for its researchers' previous experience in working with HIV-positive crack cocaine users. The first network-related study will evaluate an intervention intended to link and retain HIV-infected substance abusers in care and treatment, and eventually to decrease their viral load and risk of transmission. 

Atlanta Journal-Constitution     (10.07.10)

New HIV Cases Top One Thousand Again

New diagnoses of HIV in Australia reached 1,050 in 2009, the continuation of a decade-long climb and the highest figure in almost two decades.

"It's fair to say over the last decade there was a substantial increase and we are starting to stabilize out, just recently," said Dr. David Wilson, of the National Center in HIV Epidemiology and Clinical Research.

The climb in HIV diagnoses comes amid mixed success in addressing other STDs. Chlamydia diagnoses rose 4 percent in 2009 to 62,613. At the same time, rates of gonorrhea and syphilis improved as did the incidence of hepatitis C. Among those 15 to 19 years of age, a drop in injecting drug use is credited with lowering cases of hepatitis C by 80 percent in the last five years.

Wilson attributed the rise in HIV diagnoses to the fact that improved treatment has made the disease "not as scary as it was in the 1980s."

While HIV diagnoses are increasing, mortality from HIV has declined since the 1990s. In 2009, nine deaths in Australia were attributed to AIDS, down from 26 in 2008.

"We are in an era where we are seeing the lowest deaths associated with HIV than we have seen in history," Wilson said.

About 25 percent of the HIV-positive population is 55 or older, compared to 2.5 percent in 1985 and the 44 percent expected in 10 years, Wilson said.
Australian Associated Press     (10.18.10):: Danny Rose

Fighting HIV Among Inmates

he National Institutes of Health (NIH) is funding its first initiative to fight HIV in correctional facilities with $50 million in grants over the next five years.

The research grants, awarded by the NIH's National Institute on Drug Abuse (NIDA), will be distributed to organizations in several states, including Illinois.

"If you don't tackle these hard-to-reach populations, there's enough of them to sustain the epidemic," said Dr. Jacques Normand, director of NIDA's AIDS research program.

In Illinois, $7 million will cover three main initiatives: revamping HIV testing in prisons, examining the use of telemedicine for HIV-positive inmates, and keeping closer ties with HIV-positive inmates once they leave prison.

Illinois prison officials will use the grant money to establish routine HIV testing on those entering the system unless an inmate opts out. Cook County Jail will switch to an opt-out approach this month.

The switch to routine testing is consistent with CDC guidelines and is expected to slash the number of inmates who are unaware of their HIV status, said Dr. Jeremy Young, an infectious-disease specialist with the University of Illinois at Chicago (UIC) and one of three lead investigators on the project.

In the telemedicine research project, investigators will examine a two-month-old pilot project involving UIC and the Illinois Department of Corrections. While a nurse is in the room with a patient, an HIV specialist examines the patient with the help of a camera and remote stethoscope.

"It's basically just like a live visit," Young said.

To help keep track of HIV-positive inmates when they leave prison, the grant provides for additional case managers who help inmates secure mental health services, drug counseling, and participation in the state's AIDS Drug Assistance Program.

Chicago Sun-Times     (10.12.10):: Monifa Thomas

1 in 22 Blacks Will Get HIV, CDC Report Says

A new CDC report estimating the lifetime risk of HIV diagnosis for several populations found great disparities by racial/ethnic groups. Based on HIV surveillance, vital statistics, and census data from 37 states and Puerto Rico for 2007, an estimated 4.65 percent of blacks/African Americans would receive an HIV diagnosis during their lifetime, or 1 in 22, according to the new report.

The 1 in 22 risk was more than twice the estimated lifetime risk of HIV diagnosis for Hispanics/Latinos (1.92 percent, or 1 in 52) and eight times that of whites (0.59 percent, or 1 in 170), the report found.

The estimates of lifetime risk of HIV diagnosis are not representative of all HIV diagnoses in the United States. However, the data also were not considered unusual. A report published in 2008 found a similar high estimated lifetime risk of HIV diagnosis for blacks.

The new report, "Estimated Lifetime Risk for Diagnosis of HIV Infection Among Hispanics/Latinos - 37 States and Puerto Rico, 2007," was published in Morbidity and Mortality Weekly Report (2010;59(40):1297-1301).

Colorado State University Gets Funding to Validate Tuberculosis Treatment Test

The US Food and Drug Administration awarded Colorado State University almost $500,000 to continue studies on a test that measures molecules in urine to determine whether TB treatment is working. The researchers look for large decreases in more than 50 small molecules present in the urine at the time of diagnosis. At present, doctors cannot tell whether treatment is effective until about two months after a patient has been taking antituberculosis drugs. According to principal investigator John Belisle, the researchers have identified a series of metabolites in TB patients’ urine that disappear or decrease in abundance when the patients respond to antituberculosis treatment.  The grant would enable the scientists to continue working on the test so it can be used in clinical trials for new TB treatments, as well as predict whether or not patients will redevelop TB after completing treatment.
Colorado State University, www.news.colostate.edu, October 11, 2010, by Dell Rae Moellenberg, DellRae.Moellenberg@ColoState.EDU,

University of Georgia Gets Part of $2.9 Million Federal Grant to Study TB

A scientist at the University of Georgia is among the recipients of a $2.9 million US Food and Drug Administration grant for TB research. Frederick D. Quinn of the College of Veterinary Medicine hopes to develop an improved diagnostic test for latent TB. While about 9 - 14 million people have active TB disease globally, 2 billion have latent TB infection, Quinn said. The grant will be divided among six researchers, and Quinn’s share is $742,498 over two years.
Associated Press, October 8, 2010