Certain diseases, birth defects may be linked to failure of protein recycl...(. In a series of experiments with ge...)

In a series of experiments with genetically engineered cells from the fruit fly Drosophila, mice and humans, Dr. Lin and his colleagues mutated the Vps35 trafficking protein to compromise its central assembly role in the Retromer Complex, then observed the delivery cycle of Wnt proteins between the Trans-Golgi Network and targeted cell sites. In all three series, the compromised Retromer Complex resulted in Wnt protein accumulating in the Trans-Golgi Network and Wls cargo receptors being degraded instead of returning to the network and their job of delivering Wnt proteins.

Although we propose that the Wls protein acts as a cargo receptor for Wnt signaling proteins, we need to conduct more experiments to further our understanding of this process, including how the Wls delivers Wnt from the Trans-Golgi, Dr. Lin said.

In their study, the researchers proposed a delivery cycle model where Wnt initially enters the Trans-Golgi Network and binds with the Wls cargo receptor, which then transports Wnt to targeted cell surfaces. Once Wls has delivered Wnt proteins, one of two things occurs, depending on whether the Retromer Complex is functioning normally. When working as designed, the Retromer Complex retrieves the spent Wls protein for return to the Trans-Golgi. When Retromer Complex breaks down, Wls cargo receptor is absorbed into the cells lysosome, where it is digested and destroyed.

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