Researchers uncover how cell membrane composition drives most cancers proliferation

Cells are enveloped by a lipid membrane that provides them construction and offers a barrier between the cell and its surroundings. Nevertheless, proof has lately emerged suggesting that these membranes do greater than merely present safety – in addition they affect the habits of the protein receptors embedded in them.

A brand new examine from MIT chemists provides additional assist to that concept. The researchers discovered that altering the composition of the cell membrane can alter the operate of a membrane receptor that promotes proliferation.

Epidermal progress issue receptor (EGFR) may be locked into an overactive state when the cell membrane has the next than regular focus of negatively charged lipids, the researchers discovered. This will likely assist to clarify why most cancers cells with excessive ranges of these lipids enter a extremely proliferative state that enables them to divide uncontrollably.

The longstanding dogma of what a membrane does is that it is only a scaffold, an organizational construction. Nevertheless, there have been rising observations that counsel that perhaps these membrane lipids are literally enjoying a task in receptor operate.” 

Gabriela Schlau-Cohen, the Robert T. Haslam and Bradley Dewey Professor of Chemistry at MIT and the senior creator of the examine

The findings open up the potential for discovering new methods to deal with tumors by neutralizing the detrimental cost, which could flip down EGFR signaling, she provides.

Shwetha Srinivasan PhD ’22 is the lead creator of the paper, which seems within the journal eLife. Different authors embody former MIT postdocs Xingcheng Lin and Raju Regmi, Xuyan Chen PhD ’25, and Bin Zhang, an affiliate professor of chemistry at MIT.

Receptor dynamics

The EGF receptor, which is discovered on cells that line physique surfaces and organs, is considered one of many receptors that assist management cell progress. Some sorts of most cancers, particularly lung most cancers and glioblastoma, overexpress the EGF receptor, which might result in uncontrolled progress.

Like most receptor proteins, EGFR spans your complete cell membrane. Till lately, it has been difficult to check how indicators are conveyed throughout your complete receptor, due to the problem of making membranes which have proteins going during them after which learning each ends of these proteins.

To make it simpler to check these signaling processes, Schlau-Cohen’s lab makes use of nanodiscs, a particular sort of self-assembling membrane that mimics the cell membrane. When making these discs, the researchers can embed receptors in them, permitting the staff to check the operate of the full-length receptor.

Utilizing a way referred to as single molecule FRET (fluorescence resonance vitality switch), the researchers can examine how the form of the receptor modifications beneath completely different situations. Single molecule FRET permits them to measure the space between completely different components of the protein by labeling them with fluorescent tags after which measuring how briskly vitality travels between the tags.

In earlier work, Schlau-Cohen and Zhang used single molecule FRET and molecular dynamics simulations to disclose what occurs when EGFR binds to EGF. They discovered that this binding causes the transmembrane part of the receptor to alter form, and that shape-shift triggers the part of the receptor that extends contained in the cell to activate mobile equipment that stimulates progress.

Caught in an overactive state

Within the new examine, the researchers used an identical strategy to analyze how altering the composition of the membrane impacts the operate of the receptor. First, they explored how elevated ranges of negatively charged lipids would have an effect on the cell membrane and EGFR operate.

Usually, about 15 p.c of the cell membrane is made up of negatively charged lipids. The researchers discovered that membranes with negatively charged lipids within the vary of 15 to 30 p.c behaved usually, but when that stage reached 60 p.c, then the EGFR receptor would turn into locked into an energetic state.

In that state, the pro-growth signaling pathway is turned on on a regular basis, even when no EGF is certain to the receptor. Many most cancers cells present elevated ranges of those lipids, and this mechanism may assist to clarify why these cells are in a position to develop unchecked, Schlau-Cohen says.

“If the membrane has excessive ranges of negatively charged lipids, then it is all the time in that open conformation. It would not matter if ligand is certain or unbound,” she says. “It is all the time within the conformation that is telling the cell to develop, not simply when EGF binds.”

The researchers additionally used this method to discover the position of ldl cholesterol in EGFR operate. When the researchers created nanodiscs with elevated levels of cholesterol, they discovered that the membranes turned extra inflexible, and this rigidity suppressed EGFR signaling.

The analysis was funded by the Nationwide Institutes of Well being and MIT’s Division of Chemistry.