INSULIN PATHWAY

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INSULIN PATHWAY
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THE BETA CELLS
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GLUT TRANSPORTERS

• 4 Types (1-4)
• GLUT 2 (pancreas not insulin sensitive)
• GLUT 4 (muscles, fat tissue insulin sensitive)

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1.GLUCOSE RESPONSE

• Glucose binds to GLUT2
• Initiates signal transduction
• Activates transcription factors for insulin
  production

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• NUCLEUS here transcription factors promote the
  transcription of the insulin gene into mRNA
• RER here mRNA is translated into pre-proinsulin
  (100 a.a.)

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• pre component is cleaved off RER ? proinsulin
  (approx. 81 a.a.)
• Sent to golgi via microtubule network in vesicles

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• C. Golgi Complex responsible for final
  maturation to insulin by removing pro component
• - packaged in vesicles awaiting exocytosis

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2. Glucose Response 2

• Previously made pro-insulin in vesicles
• Maturation ? insulin
• Signal transduction ? Ca2 influx ? exocytosis

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• Glucose conv. Into energy to produce ATP in
  mitochondria
• High ATP blocks K-channel
• Alters voltage and opens Ca2 channel
• Ca2 triggers exocytosis

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RECYCLING OF COMPONENTS

• membrane components, secretory vesicles
  receptors are recycled within Lysosomes

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WHAT DOES INSULIN DO?

• Promotes inc. of GLUT4 transporters
• Muscles ? glycogen synthase activation
• Adipose ? fat storage

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