Insulin and hypertonicity recruit GLUT4 to the plasma membrane of muscle cells by using N-ethylmaleimide-sensitive factor-dependent SNARE mechanisms but different v-SNAREs: role of TI-VAMP.
Insulin and hypertonicity each increase the content of GLUT4 glucose transporters at the surface of muscle cells. Insulin enhances GLUT4 exocytosis without diminishing its endocytosis. The insulin but not the hypertonicity response is reduced by tetanus neurotoxin, which cleaves vesicle-associated membrane protein (VAMP)2 and VAMP3, and is rescued upon introducing tetanus neurotoxin-resistant VAMP2. Here, we show that hypertonicity enhances GLUT4 recycling, compounding its previously shown ability to reduce GLUT4 endocytosis. To examine whether the canonical soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) mechanism is required for the plasma membrane fusion of the tetanus neurotoxin-insensitive GLUT4 vesicles, L6 myoblasts stably expressing myc-tagged GLUT4 (GLUT4myc) were transiently transfected with dominant negative N-ethylmaleimide-sensitive factor (NSF) (DN-NSF) or small-interfering RNA to tetanus neurotoxin-insensitive VAMP (TI-VAMP siRNA). Both strategies markedly reduced the basal level of surface GLUT4myc and the surface gain of GLUT4myc in response to hypertonicity. The insulin effect was abolished by DN-NSF, but only partly reduced by TI-VAMP siRNA. We propose that insulin and hypertonicity recruit GLUT4myc from partly overlapping, but distinct sources defined by VAMP2 and TI-VAMP, respectively.
Programme in Cell Biology, The Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada.
Varinder K
VK
Randhawa
Farah S L
FS
Thong
Dawn Y
DY
Lim
Dailin
D
Li
Rami R
RR
Garg
Rachel
R
Rudge
Thierry
T
Galli
Assaf
A
Rudich
Amira
A
Klip
D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism*; D032342:Muscle Cells / Q000166:cytology / Q000378:metabolism*; D009122:Muscle Hypertonia / Q000378:metabolism* / Q000473:pathology; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D032446:Myoblasts / Q000166:cytology / Q000378:metabolism; D009498:Neurotoxins / Q000494:pharmacology; D050683:R-SNARE Proteins; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D050600:SNARE Proteins; D033921:Vesicular Transport Proteins / Q000378:metabolism*
D051275:Glucose Transporter Type 4; D007328:Insulin; D008565:Membrane Proteins; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D009498:Neurotoxins; D050683:R-SNARE Proteins; D011994:Recombinant Proteins; D050600:SNARE Proteins; C495694:Slc2a4 protein, rat; D033921:Vesicular Transport Proteins; D005033:Ethylmaleimide