TY - JOUR

T1 - Large GLUT4 vesicles are stationary while locally and reversibly depleted during transient insulin stimulation of skeletal muscle of living mice: imaging analysis of GLUT4-enhanced green fluorescent protein vesicle dynamics.

AU - Lauritzen, Hans P M M

AU - Galbo, Henrik

AU - Brandauer, Josef

AU - Goodyear, Laurie J

AU - Ploug, Thorkil

N1 - Keywords: Animals; Cell Nucleus; Genes, Reporter; Glucose; Glucose Transporter Type 4; Green Fluorescent Proteins; Image Processing, Computer-Assisted; Insulin; Male; Mice; Mice, Inbred C57BL; Muscle, Skeletal; Recombinant Fusion Proteins; Sarcolemma; Transfection

PY - 2007

Y1 - 2007

N2 - OBJECTIVE: Insulin stimulates glucose transport in skeletal muscle by GLUT4 translocation from intracellular compartments to sarcolemma and t-tubules. We studied in living animals the recruitment of GLUT4 vesicles in more detail than previously done and, for the first time, analyzed the steady-state recycling and subsequent re-internalization of GLUT4 on an insulin bolus. RESEARCH DESIGN AND METHODS: A confocal imaging technique was used in GLUT4-enhanced green fluorescent protein-transfected superficial muscle fibers in living mice. RESULTS: During the first 30 min of insulin stimulation, very few superficially or deeply located GLUT4 storage vesicles (>1 microm) moved in toto. Rather, big vesicles were stationary in their original position at sarcolemma or t-tubules and were locally depleted of GLUT4 by budding off of smaller vesicles. Photobleaching experiments revealed that during initial translocation and steady-state recycling, GLUT4 microvesicles (<1 microm) move from perinuclear GLUT4 depots out along the plasma membrane. Furthermore, after photobleaching of t-tubule areas, recovery of GLUT4 was slow or absent, indicating no recycling of GLUT4 from perinuclear or adjacent (1 microm) or more distant (20 microm) t-tubule areas. During waning of insulin effect, GLUT4 was re-internalized to basal stores with a delay in t-tubules compared with sarcolemma, probably reflecting delayed disappearance of insulin from t-tubules. CONCLUSIONS: In skeletal muscle, insulin reversibly stimulates local depletion of GLUT4 storage vesicles at sarcolemma and t-tubules rather than inducing movement of intact storage vesicles. During steady-state stimulation, recycling of GLUT4-containing microvesicles over longer distances (10-20 microm) takes place between perinuclear depots and sarcolemma but not at t-tubules.

AB - OBJECTIVE: Insulin stimulates glucose transport in skeletal muscle by GLUT4 translocation from intracellular compartments to sarcolemma and t-tubules. We studied in living animals the recruitment of GLUT4 vesicles in more detail than previously done and, for the first time, analyzed the steady-state recycling and subsequent re-internalization of GLUT4 on an insulin bolus. RESEARCH DESIGN AND METHODS: A confocal imaging technique was used in GLUT4-enhanced green fluorescent protein-transfected superficial muscle fibers in living mice. RESULTS: During the first 30 min of insulin stimulation, very few superficially or deeply located GLUT4 storage vesicles (>1 microm) moved in toto. Rather, big vesicles were stationary in their original position at sarcolemma or t-tubules and were locally depleted of GLUT4 by budding off of smaller vesicles. Photobleaching experiments revealed that during initial translocation and steady-state recycling, GLUT4 microvesicles (<1 microm) move from perinuclear GLUT4 depots out along the plasma membrane. Furthermore, after photobleaching of t-tubule areas, recovery of GLUT4 was slow or absent, indicating no recycling of GLUT4 from perinuclear or adjacent (1 microm) or more distant (20 microm) t-tubule areas. During waning of insulin effect, GLUT4 was re-internalized to basal stores with a delay in t-tubules compared with sarcolemma, probably reflecting delayed disappearance of insulin from t-tubules. CONCLUSIONS: In skeletal muscle, insulin reversibly stimulates local depletion of GLUT4 storage vesicles at sarcolemma and t-tubules rather than inducing movement of intact storage vesicles. During steady-state stimulation, recycling of GLUT4-containing microvesicles over longer distances (10-20 microm) takes place between perinuclear depots and sarcolemma but not at t-tubules.

U2 - 10.2337/db06-1578

DO - 10.2337/db06-1578

M3 - Journal article

C2 - 17977960

VL - 57

SP - 315

EP - 324

JO - Diabetes

JF - Diabetes

SN - 0012-1797

IS - 2

ER -