Antimicrobial PeptidesAntimicrobial Peptides

An ancient immune system?An ancient immune system?

oror

This frog could save This frog could save youryour leg leg

Huh?

Antimicrobial peptides:Antimicrobial peptides:Where are they?Where are they?

In everything from Amoebas to HumansIn everything from Amoebas to Humans Abundant in vertebrates in: Abundant in vertebrates in: • External MucosaExternal Mucosa– eyes, mouth, genitourinary, skin, lung, tracheaeyes, mouth, genitourinary, skin, lung, trachea

• Immune cellsImmune cells– neutrophilsneutrophils

• Intestinal tract (duodenum)Intestinal tract (duodenum)– in humans; Paneth cells are the sourcein humans; Paneth cells are the source

Cationic, AmphipathicCationic, Amphipathic• Linear Linear -helical (20-35 AA)-helical (20-35 AA)

–Magainin, cecropins, histatinMagainin, cecropins, histatin

• Pro-Arg rich (more polar)Pro-Arg rich (more polar)– bac 5 and 7 (30-50 AA; 70% pro/arg)bac 5 and 7 (30-50 AA; 70% pro/arg)

• Disulfide Rich Disulfide Rich -structure-structure– amoebapores, NK-lysinamoebapores, NK-lysin

• Disulfide Rich Disulfide Rich -structure-structure– Defensins: three or more disulfide (30-70 AA)Defensins: three or more disulfide (30-70 AA)– “ “Loops” (11-22 AA)Loops” (11-22 AA)

• tachpyylesins, protegrins ,ranalexin, polymyxintachpyylesins, protegrins ,ranalexin, polymyxin

Antimicrobial peptides:Antimicrobial peptides:What are they?What are they?

HUMAN HUMAN PLANT PLANT

Defensin-likeDefensin-like

Helical: PGLa(frog)Helical: PGLa(frog)

Small ProteinsSmall Proteins• lysozymelysozyme• phospholipase aphospholipase a• cathepsinscathepsins

Antimicrobial peptides:Antimicrobial peptides:What are they?What are they?

AntifungalAntifungal AntibacterialAntibacterial• Gram positiveGram positive

• Gram negativeGram negative

Antimicrobial peptides:Antimicrobial peptides:What do they do?What do they do?

cell wall cell wall

cell wall cell wall

OMOM

LPSLPS

membranemembrane

membranemembrane

Permeabilize OM, IMPermeabilize OM, IM• channelschannels• lysislysis

– D-analogs sometimes as effectiveD-analogs sometimes as effective

Carry LPSCarry LPS• immune stimulation?immune stimulation?

Enzyme actionEnzyme action• cell wall destructioncell wall destruction• lipase , proteaselipase , protease

– synergistic w/cationic peptides?synergistic w/cationic peptides?

Antimicrobial peptides:Antimicrobial peptides:What do they do?What do they do?

Bacteria have :Bacteria have :• more negative chargemore negative charge– recall: peptides are cationicrecall: peptides are cationic

• no sterols, little phosphatidylcholine or SMno sterols, little phosphatidylcholine or SM• a lot of PG/PE/cardiolipin/PSa lot of PG/PE/cardiolipin/PS– some tumor cells too!some tumor cells too!

Antimicrobial peptides:Antimicrobial peptides:Why are they picky?Why are they picky?

NFNFB-type genetic element seems B-type genetic element seems universaluniversal• like acute phase response in humanslike acute phase response in humans

Protective anionic piece is common,Protective anionic piece is common,

Antimicrobial peptides:Antimicrobial peptides:How are they made?How are they made?

signalsignal propiecepropiece maturemature

Mechanisms?Mechanisms?

Indolicidin analog fights test infectionsIndolicidin analog fights test infections• IP or IVIP or IV

Protegrin analog Protegrin analog • helps chemotherapy oral mucositishelps chemotherapy oral mucositis

Magainin analog, LOCILEX™ Cream underwent Magainin analog, LOCILEX™ Cream underwent clinical trials (now Genaera Corporation )clinical trials (now Genaera Corporation )• diabetic ulcers, not approveddiabetic ulcers, not approved• Squalamine, amino sterol cationic peptide analog-Squalamine, amino sterol cationic peptide analog-

anti-obesity and anti angiogenesisanti-obesity and anti angiogenesis

Antimicrobial peptides:Antimicrobial peptides:New Clinical Antibiotics?New Clinical Antibiotics?

Proteolysis, Salt, Transport propertiesProteolysis, Salt, Transport properties ManufactureManufacture

– chemical synthesis is very chemical synthesis is very expensive;$100’s/gram!expensive;$100’s/gram!

– organic mimics or modular design may helporganic mimics or modular design may help–May be possible to produce in bacteria or May be possible to produce in bacteria or

plantsplants• protective piece for bacteriaprotective piece for bacteria• TMV with tobacco (GENEWARETMV with tobacco (GENEWARE®®))

Antimicrobial peptides:Antimicrobial peptides:Problems with use?Problems with use?