TBC1D15 affects glucose uptake by regulating GLUT4 translocation.

Area of Science:

• Cell biology
• Molecular biology
• Physiology

Background:

• Glucose uptake in skeletal muscle is crucial for metabolic homeostasis.
• This process relies on the translocation of glucose transporter type 4 (GLUT4) vesicles to the cell membrane.
• Rab proteins are essential regulators of vesicle trafficking, including GLUT4.
• TBC1D15, a protein with Rab GTPase-activating protein (Rab-GAP) activity, has been implicated in vesicle regulation.

Purpose of the Study:

• To investigate the role of TBC1D15 in regulating GLUT4 translocation and glucose uptake.
• To elucidate the specific pathway through which TBC1D15 influences GLUT4 trafficking.

Main Methods:

• CRISPR/Cas9 gene editing was used to generate TBC1D15 knockout cells (TBC1D15-/-).
• Glucose uptake was measured using the fluorescent glucose analog 2-NBDG.
• Immunofluorescence microscopy was employed to assess the localization and co-localization of GLUT4, Rab7, and Lamp1.

Main Results:

• TBC1D15 knockout led to a significant reduction in 2-NBDG uptake, indicating impaired glucose transport.
• Total GLUT4 protein levels were significantly decreased in TBC1D15-/- cells compared to wild-type (WT) cells.
• Rab7 accumulated in late endosomes/lysosomes (Lamp1-positive compartments) in TBC1D15-/- cells.
• Increased co-localization between GLUT4 and Rab7 was observed in TBC1D15-/- cells, suggesting altered trafficking through the late endosomal pathway.

Conclusions:

• TBC1D15 acts as a key regulator of GLUT4 translocation via the late endosomal pathway.
• The absence of TBC1D15 disrupts normal GLUT4 trafficking, leading to reduced glucose uptake.
• TBC1D15 plays a critical role in controlling glucose metabolism in skeletal muscle.