Insights into Human Growth Hormone and Its Medical Applications

 
Human Growth Hormone
 
Growth hormone (somatotropin)  size 191 amino
acids mol wt. 22125 kd is secreted by Anterior
Pituitary
 
Growth hormone stimulates production of
insulin-like growth factor 1.
 
Insulin-like growth factor 1 is an essential
component of the promotion of growth in
children, and in adults
 
It controls metabolism
 
Infants and children who lack sufficient endogenous levels
of human growth hormone
Patients with chronic renal insufficiency (defective
kidneys),
Turner syndrome
Respond to treatment with growth hormone
 
It stimulates
Tissue and bone growth,
increases protein synthesis
Mineral retention
Decreases body fat storage
 
In 1982, human insulin became the first
pharmaceuticals  produced by recombinant DNA
technologies for commercial use.
 
Since then, several other human proteins with
medicinal value have been synthesized in bacteria.
Some of the first human proteins to be produced in
microorganisms were :
 
Blood-clotting factor VIII (lacking in individuals
with one type of hemophilia)
Plasminogen activator (a protein that disperses
blood clots)
Human growth hormone (a protein deficient in
certain types of dwarfism).
 
In 1985, hGH became the second genetically
engineered pharmaceutical approved for use in
humans by the U.S. Food and Drug Administration.
 
The first recombinant growth hormone was called
somatrem (Protropin)
 
It had an amino acid sequence that was identical to
that of human growth hormone, except that there was
an extra methionine residue at the N-terminal end of
the peptide chain
 
Only growth hormones from humans or from closely
related primates will function in humans.
 
Thus, prior to 1985, the major source of growth
hormone suitable for treatment of humans was from
human cadavers
 
hGH, which is required for normal growth, is a single
polypeptide chain 191 amino acids in length
 
To obtain expression in 
E. coli, 
the hGH coding
sequence must be placed under the control of 
E.
coli 
regulatory elements.
 
Therefore, the hGH coding sequence was joined to
the promoter and ribosome-binding sequences of
the 
E. coli lac 
operon
 
To accomplish this, a 
Hae
III cleavage site in the
nucleotide-pair triplet specifying codon 24 of hGH
was used to fuse a synthetic DNA sequence encoding
amino acids 1–23 to a partial cDNA sequence
encoding amino acids 24–191.
 
This unit was then inserted into a plasmid carrying
the 
lac 
regulatory signals and introduced into 
E. coli
by transformation
 
The hGH produced in 
E. coli 
in these first experiments
contained methionine at the amino terminus (the
methionine specified by the ATG initiator codon).
Native hGH has an amino-terminal phenylalanine: a
methionine is initially present but is then enzymatically
removed.
 
E. coli 
also removes many amino-terminal methionine
residues posttranslationally. However, the excision of the
terminal methionine is sequence-dependent, and 
E. coli
cells do not excise the amino-terminal methionine residue
from hGH.
 
Nevertheless, the hGH synthesized in 
E. coli 
was found to
be fully active in humans despite the presence of the extra
amino acid.
 
More recently, a DNA sequence encoding a signal peptide
(the amino acid sequence required for transport of
proteins across membranes) has been added to an hGH
gene construct.
With the signal sequence added, hGH is both secreted
and correctly processed The methionine residue is
removed with the rest of the signal peptide during the
transport of the primary translation product across the
membrane.
 
This product is identical to native hGH.
 
in 2004, the U.S. Food and Drug Administration (FDA)
approved the use of recombinant human growth
hormone for individuals whose short stature was caused
by a variety of medical conditions other than human
growth hormone deficiency.
 
Native human growth hormone binds to both growth hormone
and prolactin receptors that occur on a number of different cell
types.
 
To avoid unwanted side effects during therapy, it is desirable
that human growth hormone bind only to growth hormone
receptors.
 
Site-specific mutagenesis of the cloned human growth
hormone cDNA was used to change some of the amino acid
side chains that act as ligands for Zn
2+ 
(i.e., His-18, His-21, and
Glu-174), because the ion is required for the high-affinity
binding of human growth hormone to the prolactin Receptor
 
These modifications yielded human growth hormone
derivatives that bound to the growth hormone receptor but not
to the prolactin receptor.
 
Short half-life in plasma, human growth hormone therapy
currently requires subcutaneous injection once a day.
 
This treatment is both inconvenient and expensive.
 
The extracellular domain of the human growth hormone
receptor was fused to human growth hormone
 
This construct has a very strong tendency to dimerize as the
growth hormone moiety from one molecule binds with the
receptor portion of another molecule.
 
When this growth hormone construct was tested in rats, a
single injection promoted growth for 10 days
 
Another method that has been devised to prolong the
active lifetime of human growth hormone includes fusing
the coding sequences for the C-terminal end of human
growth hormone  with the N-terminal end of human serum
albumin. This fusion protein is called Albutropin
 
The stabilization of the human growth hormone portion of
Albutropin reflects the stability of human serum albumin,
which has a half-life in serum of about 19 days.
Slide Note
Embed
Share

Human Growth Hormone (HGH), a key hormone secreted by the anterior pituitary gland, plays a crucial role in stimulating growth and metabolism. Its therapeutic applications range from treating growth hormone deficiency in children to genetic engineering for pharmaceutical production. HGH has made significant contributions to medical advancements, especially in tackling hormonal imbalances and promoting growth in both children and adults.


Uploaded on Aug 03, 2024 | 0 Views


Download Presentation

Please find below an Image/Link to download the presentation.

The content on the website is provided AS IS for your information and personal use only. It may not be sold, licensed, or shared on other websites without obtaining consent from the author. Download presentation by click this link. If you encounter any issues during the download, it is possible that the publisher has removed the file from their server.

E N D

Presentation Transcript


  1. Human Growth Hormone

  2. Growth hormone (somatotropin) size 191 amino acids mol wt. 22125 kd is secreted by Anterior Pituitary Growth hormone stimulates production of insulin-like growth factor 1. Insulin-like growth factor 1 is an essential component of the promotion of growth in children, and in adults It controls metabolism

  3. Infants and children who lack sufficient endogenous levels of human growth hormone Patients with chronic renal insufficiency (defective kidneys), Turner syndrome Respond to treatment with growth hormone It stimulates Tissue and bone growth, increases protein synthesis Mineral retention Decreases body fat storage

  4. In pharmaceuticals produced by recombinant DNA technologies for commercial use. 1982, human insulin became the first Since then, several other human proteins with medicinal value have been synthesized in bacteria. Some of the first human proteins to be produced in microorganisms were : Blood-clotting factor VIII (lacking in individuals with one type of hemophilia) Plasminogen activator (a protein that disperses blood clots) Human growth hormone (a protein deficient in certain types of dwarfism).

  5. In 1985, hGH became the second genetically engineered pharmaceutical approved for use in humans by the U.S. Food and Drug Administration. The first recombinant growth hormone was called somatrem (Protropin) It had an amino acid sequence that was identical to that of human growth hormone, except that there was an extra methionine residue at the N-terminal end of the peptide chain

  6. Only growth hormones from humans or from closely related primates will function in humans. Thus, prior to 1985, the major source of growth hormone suitable for treatment of humans was from human cadavers hGH, which is required for normal growth, is a single polypeptide chain 191 amino acids in length

  7. To obtain expression in E. coli, the hGH coding sequence must be placed under the control of E. coli regulatory elements. Therefore, the hGH coding sequence was joined to the promoter and ribosome-binding sequences of the E. coli lac operon

  8. To accomplish this, a HaeIII cleavage site in the nucleotide-pair triplet specifying codon 24 of hGH was used to fuse a synthetic DNA sequence encoding amino acids 1 23 to a partial cDNA sequence encoding amino acids 24 191. This unit was then inserted into a plasmid carrying the lac regulatory signals and introduced into E. coli by transformation

  9. The hGH produced in E. coli in these first experiments contained methionine at the amino terminus (the methionine specified by the ATG initiator codon). Native hGH has an amino-terminal phenylalanine: a methionine is initially present but is then enzymatically removed. E. coli also removes many amino-terminal methionine residues posttranslationally. However, the excision of the terminal methionine is sequence-dependent, and E. coli cells do not excise the amino-terminal methionine residue from hGH. Nevertheless, the hGH synthesized in E. coli was found to be fully active in humans despite the presence of the extra amino acid.

  10. More recently, a DNA sequence encoding a signal peptide (the amino acid sequence required for transport of proteins across membranes) has been added to an hGH gene construct. With the signal sequence added, hGH is both secreted and correctly processed The methionine residue is removed with the rest of the signal peptide during the transport of the primary translation product across the membrane. This product is identical to native hGH.

  11. in 2004, the U.S. Food and Drug Administration (FDA) approved the use of recombinant human growth hormone for individuals whose short stature was caused by a variety of medical conditions other than human growth hormone deficiency.

  12. Native human growth hormone binds to both growth hormone and prolactin receptors that occur on a number of different cell types. To avoid unwanted side effects during therapy, it is desirable that human growth hormone bind only to growth hormone receptors. Site-specific mutagenesis of the cloned human growth hormone cDNA was used to change some of the amino acid side chains that act as ligands for Zn2+ (i.e., His-18, His-21, and Glu-174), because the ion is required for the high-affinity binding of human growth hormone to the prolactin Receptor These modifications derivatives that bound to the growth hormone receptor but not to the prolactin receptor. yielded human growth hormone

  13. Short half-life in plasma, human growth hormone therapy currently requires subcutaneous injection once a day. This treatment is both inconvenient and expensive. The extracellular domain of the human growth hormone receptor was fused to human growth hormone This construct has a very strong tendency to dimerize as the growth hormone moiety from one molecule binds with the receptor portion of another molecule. When this growth hormone construct was tested in rats, a single injection promoted growth for 10 days

  14. Another method that has been devised to prolong the active lifetime of human growth hormone includes fusing the coding sequences for the C-terminal end of human growth hormone with the N-terminal end of human serum albumin. This fusion protein is called Albutropin The stabilization of the human growth hormone portion of Albutropin reflects the stability of human serum albumin, which has a half-life in serum of about 19 days.

Related


More Related Content

giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#