19/10/18
Dr Tania Maffucci
Transmembrane Signalling
37 trillion cells in the human body – 210 types
Temporal regulation – control of differentiation, division etc.
Spatial regulation – control of cell movement (chemotaxis)
Signals are specific to target cell only
• Signals converted to a series of biochemical reactions intracellular
• These are called pathways e.g. synthesis of proteins
1. Sending the Signal
• Sent by molecule extracellularly, for example a growth factor or hormone
• Released by another cell or the environment
• Gap junctions
o Signals rarely pass freely from one cell to another
o These give direct cytoplasmic communication
between adjacent cells
o 2 connexons make up the hemichannels
▪ Connexons are made up of 6 connexin
proteins
▪ In connexin proteins there are 4
transmembrane domains
▪ 24 different types of connexins in humans
o Two types of hemichannels:
▪ 1) homotypic = hemichannels in same position on cells
▪ 2) heterotypic = hemichannels in different positions
o Gap junction plaque is made up of many channels
o Not to be confused with TIGHT JUNCTIONS
• Signal sent is called a ligand
❖ Endocrine = glands that secrete products into blood
o E.g. Islets of Langerhans in pancreas
❖ Exocrine = glands that secrete products into ducts
o E.g. sweat or salivary glands
❖ Autocrine = the cell that sends the signal is the same one that receives it
❖ Paracrine = ligand acting on neighbouring cells
o E.g. juxtracrine when the ligand isn’t released, but is attached to cell so needs to be
in close proximity to target cell
Dr Tania Maffucci
Transmembrane Signalling
37 trillion cells in the human body – 210 types
Temporal regulation – control of differentiation, division etc.
Spatial regulation – control of cell movement (chemotaxis)
Signals are specific to target cell only
• Signals converted to a series of biochemical reactions intracellular
• These are called pathways e.g. synthesis of proteins
1. Sending the Signal
• Sent by molecule extracellularly, for example a growth factor or hormone
• Released by another cell or the environment
• Gap junctions
o Signals rarely pass freely from one cell to another
o These give direct cytoplasmic communication
between adjacent cells
o 2 connexons make up the hemichannels
▪ Connexons are made up of 6 connexin
proteins
▪ In connexin proteins there are 4
transmembrane domains
▪ 24 different types of connexins in humans
o Two types of hemichannels:
▪ 1) homotypic = hemichannels in same position on cells
▪ 2) heterotypic = hemichannels in different positions
o Gap junction plaque is made up of many channels
o Not to be confused with TIGHT JUNCTIONS
• Signal sent is called a ligand
❖ Endocrine = glands that secrete products into blood
o E.g. Islets of Langerhans in pancreas
❖ Exocrine = glands that secrete products into ducts
o E.g. sweat or salivary glands
❖ Autocrine = the cell that sends the signal is the same one that receives it
❖ Paracrine = ligand acting on neighbouring cells
o E.g. juxtracrine when the ligand isn’t released, but is attached to cell so needs to be
in close proximity to target cell
