Role of transverse tubules in insulin stimulated muscle glucose transport

✍ Scribed by Dr. G. Lynis Dohm; Patricia L. Dolan; Wilhelm R. Frisell; Ronald W. Dudek

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 684 KB
• Volume: 52
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/jcb.240520102

✦ Synopsis

Although the strongest evidenccl tor rc,cruitment of glucose transporters in response to insulin comes froin studies with adipocytes, studirs in muscle wem in general to confirm that gluc ose transporters dre a l w trdnslocdted to the cell membrane in muscle in rcyionse to iiiculin However, the observation that transverse tubule (r-tubule) membranes contain approximately five t i r n c s morv glucose transporter thdn sarcolemma raised a question as t o where glucose transport occurs in musclc~ Ihtl T-tubule membrane system IS continuous with the surface sarcoleinma and is a tubule system in which extracellular tluid 1 4 in proximity with the interior of the muscle tiber The purpose ot this Prospects article is to evaluate the p o i h l i t y that the T-tubule membrane may represent d major site of glucose transport in skeletal muscle Using immunocytochemicdl techniques we h a w lo( atcd LLUT3 glucose transporters on the T-tubule membrane dnd in vesic les near T-tubules Since T-tubules form c hannt4s into the interior of the muscle fiber, glucose could diffuse or be moved by some peristaltic-like pumping action into the transverse tubules and then be transported ac ross the membrane deep into the interior ot the muscle tiber This mode o i transport directly into the interior of the cell would be advantageous over transport across the sarcolemm,i ,md subwquent diffusion around the myofibrils to reach the interior ot the muscle Thus, in addition to the role 01 the T-tubule, in ion fluxes and contraction, this unique membranc system can also provide d pathway for the delivt.ry oi wbstrates into the center of the musclr cell where many glycolytic enzymes and glycogen deposits are lo( dted