In autophagy, a vesicle swallows a portion of cytoplasm and ferries it to the lysosome for digestion. The process is often beneficial, allowing hungry cells to recycle molecules, for example. However, the researchers previously discovered that in mice with pancreatitis the level of autophagy in pancreatic cells surges. Pancreatitis occurs when the enzyme trypsin dissolves cells from within. Normally, pancreatic cells fashion and discharge an inactive form of trypsin called trypsinogen, which remains inert until it reaches the small intestine. But if trypsinogen converts to trypsin before its release, it can damage or kill a pancreatic cell. Hashimoto et al. tested whether autophagy promotes this early activation by delivering trypsinogen to the lysosome, where enzymes turn it on.

The researchers gave mice injections of the compound cerulein, which spurs pancreatitis. Control animals suffered severe damage to the organ, which harbored numerous deteriorating cells. But rodents that lack a gene necessary for autophagy displayed almost no symptoms. To determine whether autophagy promotes trypsinogen activation, the team dosed pancreatic cells from both types of mice with cerulein. Cells from the autophagy-impaired animals carried much less activated trypsinogen than did cells from controls.

In rodents capable of autophagy, cerulein injections triggered much higher levels of trypsin activity in pancreatic tissue than did shots of saline, confirming that autophagy switches on the enzyme. The study is the first to reveal that autophagy can initiate a disease. The next step, the researchers say, is determining what triggers pancreatic cells to start eating themselves.

rockefeller/

In this study, the zinc finger protein brings a DNA enzyme to the CCR5 gene to cut a portion of its sequence, but due to the repair process a new mutation arises in the CCR5 protein, rendering it non-functional. Without a functional CCR5 protein on the cell's surface, HIV cannot enter, presumably leading to resistance to HIV infection.

The researchers demonstrated this process in cell culture and in a mouse model. For the animal part of the study, the investigators used healthy human CD4 T cells and added DNA that expresses the zinc fingers, which modifies the CCR5 co-receptor. They grew the engineered cells in tissue culture flasks and transferred them into immune-deficient mice infected with HIV. "We followed them over time and showed that those mice that received the zinc-finger-treated cells showed less viral load than controls and improved CD4 counts," says Perez.

The researchers are planning a clinical trial in humans in which T cells from HIV patients would have their CCR5 gene deliberately knocked out. These modified T cells could then be infused back into the patients to re-establish their immune system and decrease their viral load.

med.upenn/