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GLUT4 is an insulin-responsive glucose transporter expressed especially in skeletal muscle and adipose tissue. Insulin increases its abundance at the cell surface by regulating vesicle trafficking, thereby increasing transport capacity. GLUT4 facilitates transport down the glucose concentration difference; it does not directly pump glucose using ATP. Regulation by relocation illustrates how a cell can change transport rapidly without first synthesizing a new biological population of transporter proteins. ^[ref]

Madin-Darby canine kidney cell, used in three-dimensional epithelial cyst and polarity assays.

The cultured epithelial model can form polarized layers or epithelial cysts, making it useful for testing vesicle trafficking and apical-basal organization. Cell-line origin, culture geometry and the particular clone matter when comparing results across experiments. ^[ref]

MT1-MMP, also called MMP14, is a membrane-associated metalloprotease involved in remodelling the extracellular matrix. Surface delivery concentrates proteolytic activity at particular cellular locations, linking vesicle trafficking to matrix interactions. Altered total protein abundance and altered delivery to the surface are different routes to changing extracellular activity. This distinction matters when relating a trafficking perturbation to cell invasion. ^[ref]

The fragment might sequester another factor required for vesicle trafficking or actin organization, rather than acting through Munc18. For example, binding a different SNARE-associated protein could lower the concentration available for productive endogenous complexes. This is a possible dominant-negative effect, not evidence that the isolated N terminus contains the entire SNARE interaction surface.

A less specific alternative is cellular stress or reduced viability. Those effects could suppress both invadopodium formation and matrix degradation without selectively inhibiting the proposed trafficking pathway.

Vesicle trafficking moves membrane and cargo between cellular compartments through transport carriers. Cargo selection and budding are followed by targeting, vesicle docking and membrane fusion. A carrier from the endoplasmic reticulum can deliver newly synthesized proteins to the Golgi apparatus, while other carriers retrieve resident components. Directional transport maintains distinct compartments despite continual membrane exchange; it depends on selective recognition rather than random mixing. ^[ref]