Like brain cells, kidney cells can ‘remember’

Kidney cells can make memories too. At least, in a metaphorical sense.

Neurons have historically been the cell most associated with memory. But far outside the brain, kidney cells can also store information and recognize patterns in a similar way to neurons, researchers report November 7 in Nature Communications.

“We’re not saying that this kind of memory helps you learn trigonometry or remember how to ride a bike or stores your childhood memories,” says Nikolay Kukushkin, a neuroscientist at New York University. “This research adds to the idea of memory; it doesn’t challenge the existing conceptions of memory in the brain.”

In experiments, the kidney cells showed signs of what’s called a “massed-space effect.” This well-known feature of how memory works in the brain facilitates storing information in small chunks over time, rather than a big chunk at once.

Outside the brain, cells of all types need to keep track of stuff. One way they do that is through a protein central to memory processing, called CREB. It, and other molecular components of memory, are found in neurons and nonneuronal cells. While the cells have similar parts, the researchers weren’t sure if the parts worked the same way.

In neurons, when a chemical signal passes through, the cell starts producing CREB. The protein then turns on more genes that further change the cell, kick-starting the molecular memory machine (SN: 2/3/04). Kukushkin and colleagues set out to determine whether CREB in nonneuronal cells responds to incoming signals the same way.

The researchers inserted an artificial gene into human embryonic kidney cells. This artificial gene largely matches the naturally occurring stretch of DNA that CREB activates by binding to it — a region the researchers call a memory gene. The inserted gene also included instructions for producing a glowing protein found in fireflies.

The team then watched the cells respond to artificial chemical pulses that mimic the signals that trigger the memory machinery in neurons. “Depending on how much light [the glowing protein] produces, we know how strongly that memory gene was turned on,” Kukushkin says.

Different timing patterns of pulses resulted in different responses. When the researchers applied four, three-minute chemical pulses separated by 10 minutes, the light 24 hours later was stronger than in cells where the researchers applied a “massed” pulse, a single 12-minute pulse.

“This [massed-spaced] effect has never been seen outside a brain, it’s always been thought as this property of neurons, of a brain, how memory is formed,” Kukushkin says. “But we propose that maybe if you give nonbrain cells complicated enough tasks, they will also be able to form a memory.”

Neuroscientist Ashok Hegde calls the study “interesting, because they are applying what’s generally considered a neuroscience principle sort of broadly to understand gene expression in nonneuronal cells.” But it’s unclear how generalizable the findings are to other kinds of cells, says Hegde, of Georgia College & State University in Milledgeville. Still, he says this research may someday help with the search for potential drugs to treat human disease, especially those where memory loss occurs.

Kukushkin agrees. The body can store information, he says, and that could be meaningful to someone’s health.

“Maybe we can think of cancer cells as having memories, and think about what they can learn from the pattern of chemotherapy,” Kukushkin says. “Maybe we need to consider not just how much drug we are giving a person, but what is the time pattern of that drug, just as we think about how to learn more efficiently.”