BIOLOGY 1A03 Lecture Notes - Lecture 11: Protein Structure, Spliceosome, Blood Sugar
27 Jun 2018
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Once insulin has bound to its receptor, the conformational changes and autophosphorylation of
the receptor followed by activation of other cytoplasmic proteins induces intracellular signals
through the activation of a series of diverse transducer and amplifier proteins that are downstream
from the activated receptor.
The initiation and maintenance of a signal is regulated by
positive-feedback loops to keep the signal and amplification on.
However many elements in a signalling pathway can also
activate negative feedback loops which can lead to intracellular signal
termination.
An important feature of intracellular signaling also involves
doublenegative feedback, where an inhibitor of the signal can also be
inhibited. This provides fine control in a cell in response to an
extracellular signal.
Unit 5 – mRNA processing through alternative splicing
Regional distribution of alternate receptors
Skeletal muscles are able to absorb more than liver
From one blueprint to multiple mRNA sequencing
By regulating RNA processing, eukaryotes, are able to produce more than one mRNA transcript
from a single gene. The end result is that this allows for a single gene to encode for more than
one protein product, and thus contributes to our proteomic complexity. To produce more than one
mRNA transcript from a single protein-coding gene, alternative splicing of pre-mRNAs must occur.
Alternate splicing
Recall that exons are the regions of the premRNA that are included in the mature mRNA and that
introns are the parts of the pre-mRNA that are removed during the splicing process.
Alternative splicing enables one pre-mRNA molecule to be spliced at
different junctions to result in many different mature mRNA molecules that
each contain different combinations of transcribed exons.
During alternative splicing, some exons may be excluded during the splicing
process (being removed much like the introns), leading to the production of
many isoforms or different types of mature mRNA from the same pre-mRNA
transcript.
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BIOLOGY 1A03 Full Course Notes
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Document Summary
However many elements in a signalling pathway can also activate negative feedback loops which can lead to intracellular signal termination. (cid:120) An important feature of intracellular signaling also involves doublenegative feedback, where an inhibitor of the signal can also be inhibited. This provides fine control in a cell in response to an extracellular signal. The end result is that this allows for a single gene to encode for more than one protein product, and thus contributes to our proteomic complexity. In skeletal muscle cells, exon 11 is removed from the mature mrna product (along with the transcript introns) during the splicing process. This is an ideal insulin receptor isoform to have at skeletal muscles, since while they contribute to lowering blood glucose levels, they also allow the muscle cells to absorb enough glucose to meet their high energy needs. In contrast, liver cells produce an insulin receptor with lower affinity to insulin.
