TRANSPORTER PROTEINS PLAYED KEY ROLE IN SPECIES EVOLUTION: SAVANT

A transporter protein that regulates cell membrane cholesterol likely played an important role in vertebrate evolution, according to a review published by iCeMS researchers in the journal FEBS Letters, then online Science Daily reported.

Almost four decades of research have led scientists at Japan's Institute for Integrated Cell-Material Sciences (iCeMS) of Kyoto University to propose that a family of transporter proteins has played an important role in species evolution.

One protein in particular, called ABCA1, was likely crucial for vertebrate evolution by helping regulate when signals involved in cell proliferation, differentiation and migration enter a cell.

This process was necessary for vertebrates to develop into more complex organisms with sophisticated body structures.

The ATP-binding cassette proteins (ABC) are very similar across species, including in bacteria, plants and animals.

There are different types of ABC proteins with different transportation roles, importing nutrients into cells, exporting toxic compounds outside them, and regulating lipid concentrations within cell membranes.

Cellular biochemist Kazumitsu Ueda has studied human ABC proteins for 35 years, ever since he and his colleagues identified the first eukaryote ABC protein gene. "We believe ABC proteins must have played important roles in evolution," Ueda says. "By transporting lipids, they enabled plants and animals to thrive on land by protecting them from water loss and pathogen infection. They are also assumed to have accelerated vertebrate evolution by allowing cholesterol to function as an intra-membrane signalling molecule."

Organisms that existed early in Earth's history were probably formed of DNA and proteins surrounded by a leaky lipid membrane.

As the organisms evolved, their membranes were fortified to protect them from the external environment.

Recently, Ueda and his team studied the roles of ABCA1, gaining deeper insight into how it regulates cholesterol. Specifically, they found that ABCA1 exports cellular phospholipids and cholesterol outside the cell for generating high-density lipoproteins, popularly called good cholesterol.

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