Lecture 14: Cationic host defence peptides Flashcards
What is an alternative name for host defence peptides?
Antimicrobial peptides (AMP)
What is the function of AMPs?
To protect the host by inactivating pathogens - gram +ve, -ve, fungi, viruses- usually by disrupting the membrane.
What are some of the properties of AMPs?
Net positive charge (cationic), amphipathic to bind negative structures on membranes, produces an inflammatory response.
What are the two classes of AMP?
Cathelicidins and defensins.
What is the cathelicidin precursor hCAP18 broken down to form?
LL-37, the active peptide
In what cells is LL-37 stored?
neutrophils but also other cells such as macrophages and epithelial cells.
What are the important amino acid structures on defensins?
6 cysteines to protect from degradation by proteases, but different cysteine connectivity in the different types of defensin.
What are the three different classes of defensin?
Alpha (in the gut), beta and theta(?)
What gene encodes beta defensin?
hBD1- human B defensin 1
Which is the most effective antimicrobial B defensin gene?
hBD3
Where is hBD3 most commonly found?
In epithelial cells eg skin
How do AMPs work?
Disrupt pathogen membrane causing ions to leak out
Why do AMPs disrupt pathogen membranes but not host membranes?
Host membranes have cholesterol which protects them
How does LL-37 act as an immunomodulator?
Acts as a chemoattractant, induces histamine release, binds DNA in NETs, upreulates TLR9 and down-regulates TLR4 signalling (maybe to control immune response?)
How do defensins act as immunomodulators?
Attract DCs, mast cells, monocytes, CD4 T cells. Induce mitogenesis for wound repair.
