Alternative Splicing and Insulin Receptor Isoforms
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Questions and Answers

What role does insulin play in glucose regulation?

  • Stimulates glucose absorption by cells (correct)
  • Decreases glucose levels in the bloodstream
  • Increases blood glucose levels
  • Acts as a sensor for glucose levels

    • The genome produces a uniform set of proteins across all cells.

    False

    What type of feedback loop occurs when blood glucose levels drop?

    Negative feedback

    Alternative splicing can lead to the production of different ________ from the same gene.

    <p>isoforms</p> Signup and view all the answers

    Match the following components related to glucose regulation:

    <p>Insulin = Stimulates glucose uptake Pancreatic cells = Sense blood glucose levels Negative feedback = Reduces insulin secretion after glucose return Alternative splicing = Produces protein isoforms</p> Signup and view all the answers

    What can happen if insulin is not properly processed after translation?

    <p>Decreased glucose absorption by target tissues</p> Signup and view all the answers

    Alternative splicing leads to identical protein structures despite differences in function.

    <p>False</p> Signup and view all the answers

    What systemic response helps maintain steady state blood glucose levels after a meal?

    <p>Insulin secretion</p> Signup and view all the answers

    What mechanism helps maintain a signal in intracellular signaling?

    <p>Positive-feedback loops</p> Signup and view all the answers

    Skeletal muscles are less efficient at absorbing glucose than liver cells.

    <p>False</p> Signup and view all the answers

    What is produced through the alternative splicing of pre-mRNA?

    <p>Multiple mRNA transcripts encoding different protein products</p> Signup and view all the answers

    The regions of pre-mRNA that are included in mature mRNA are called ______.

    <p>exons</p> Signup and view all the answers

    Match the following terms related to insulin and glucose regulation:

    <p>Insulin receptor kinases = Detect blood glucose levels Adipose tissue = Stores excess as triglycerides Liver cells = Stores excess as glycogen Skeletal muscles = Absorb glucose more efficiently</p> Signup and view all the answers

    What is the primary function of the insulin receptor upon binding insulin?

    <p>Autophosphorylation and activation of proteins</p> Signup and view all the answers

    Double-negative feedback involves an inhibitor of the signal being inhibited.

    <p>True</p> Signup and view all the answers

    The parts of the pre-mRNA that are removed during splicing are called ______.

    <p>introns</p> Signup and view all the answers

    What is the primary function of alternative splicing?

    <p>To produce multiple mRNA isoforms from a single pre-mRNA transcript</p> Signup and view all the answers

    Exon 11 is excluded during the splicing of the insulin receptor gene in liver cells.

    <p>False</p> Signup and view all the answers

    What is the result of excluding exon 11 during the splicing of the insulin receptor gene in muscle cells?

    <p>A higher affinity version of the insulin receptor</p> Signup and view all the answers

    Alternative splicing leads to the production of different types of mature mRNA that can result in various ________ of proteins.

    <p>isoforms</p> Signup and view all the answers

    Match the following cell types with their corresponding insulin receptor affinity:

    <p>Skeletal Muscle Cells = Higher affinity Liver Cells = Lower affinity</p> Signup and view all the answers

    Which of the following best describes the role of the spliceosome?

    <p>It removes introns and joins exons in pre-mRNA.</p> Signup and view all the answers

    Different mRNA isoforms can be produced from the same pre-mRNA transcript in different cell types.

    <p>True</p> Signup and view all the answers

    The insulin receptor gene has a total of ________ exons.

    <p>22</p> Signup and view all the answers

    Study Notes

    Alternative Splicing

    • Pre-mRNA can be spliced at different junctions resulting in many different mature mRNA molecules, each with different combinations of exons
    • Some exons may be excluded during splicing, leading to the production of multiple protein isoforms from the same pre-mRNA transcript
    • The spliceosome may recognize an exon in one primary transcript, but an intron in other transcripts
    • The same cell can produce alternate splicing forms, or different cell types could produce different forms
    • The alternative splicing helps in regulation of gene expression, since the same primary transcript can be spliced in different ways to produce mature mRNA isoforms that code for different but related proteins

    Insulin Receptor Isoform

    • The insulin receptor gene has 22 exons
    • In skeletal muscle cells, exon 11 is removed during splicing, resulting in a higher affinity insulin receptor
    • This allows skeletal muscle cells to mount a higher response of glucose uptake to an insulin signal
    • Liver cells produce an insulin receptor with lower affinity for insulin
    • In liver cells, exon 11 is retained in the mature mRNA molecule

    Regulation of Glucose Uptake

    • Blood glucose levels are fine-tuned to maintain steady state
    • After a meal, blood glucose levels rise, but the body responds by returning to resting blood glucose levels
    • Insulin acts as an effector signal to target cells to absorb glucose from the bloodstream and regulate its uptake
    • Once blood glucose levels return to rest, the system receives negative feedback to bring it back to a starting point
    • The drop in blood glucose levels is detected by the pancreatic cells, resulting in a decrease in insulin secretion
    • This negative feedback limits further response in the system

    Proteome Diversity

    • The human genome is made up of four nucleotides, but the proteome is diverse
    • The diversity of cellular proteins contributes to the complexity and interactions that underlie cellular processes
    • Any change to alternative splicing mechanisms or post-translational modifications of proteins can lead to detrimental effects
    • If the insulin protein is not processed correctly after translation, it may not be able to bind to insulin receptors on target tissues
    • Insulin receptor is encoded by a single gene, but alternate splicing results in two isoforms

    Signaling Pathway

    • When insulin binds to its receptor, the conformation changes and the receptor autophosphorylates
    • This activates other cytoplasmic proteins and induces intracellular signals
    • Diverse transducer and amplifier proteins downstream of the receptor are activated
    • Positive feedback loops keep the signal and amplification going
    • Negative feedback loops can terminate the signal
    • Double-negative feedback can fine-tune control in the cell in response to an extracellular signal
    • This allows tissues to detect changes in blood glucose levels and contribute to the absorption of glucose from the blood
    • Fat cells take up glucose and fatty acids, storing it as triglycerides
    • The liver and muscle cells take up glucose and store it as glycogen
    • There is variable efficiency in glucose absorption

    Pre-mRNA Processing

    • Eukaryotes can produce more than one mRNA transcript from a single gene
    • This allows a single gene to encode for more than one protein product, contributing to proteomic complexity
    • Pre-mRNA transcripts are processed in the nucleus before being released as mature mRNA into the cytosol
    • Alternative splicing of pre-mRNAs occurs to produce more than one mRNA transcript from a single gene
    • Exons are the regions of the pre-mRNA included in the mature mRNA, and introns are the parts removed during splicing

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    Description

    This quiz explores the mechanisms of alternative splicing and its implications on protein isoforms, particularly focusing on the insulin receptor. Understand how different splicing can lead to variations in gene expression and functional proteins across cell types.

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