Come a little closer the venom
will hurt but you will Live, maybe…
Njeri Henderson Kristin Wright Damon Morgan Phoenix Tantum
Biology of Toxins 445
April 17th 2013
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Why should we care?
Background of Black Widow Spider (B.W.S.)
Characteristics of B.W.S.
Introduction to α-Latrotoxin (α-LTX)
Mechanism of Action
Deeper Investigations of α-LTX
Symptoms
Treatment
Toxicity Levels
Antivenin
Medical Uses
Interesting Facts
Summary
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Before you can understand the Toxin, it is useful to explore
the Animal which is responsible for it’s mechanism
There is an irrational fear of Black Widow Spiders and
exploring their Toxicity will hopefully alleviate this
assumption
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In humans α-latrotoxin RARELY result in death
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α-latrotoxin has POTENTIAL MEDICAL USES
Arachnophobia: An irrational fear of spiders and is
considered among the most common of all phobias
Of the 30,000 types of spiders, the black
widow is one of the best known and feared
Most widespread venomous land animal, ranging from the
Mediterranean, across the Americas, all of Africa and much of
Australia and in Russia and Asia.
genus: Latrodectus mactans: species
• mixture of Latin and Greek
• latro - robber / macto - to slay
translation: “deadly biting robber”
Juveniles have
more potent
venom
(more
neurotoxins)
Their venom is
15x more
potent than the
Prairie
Rattlesnake
Adult Black Widow
Juvenile Black Widow
Females
sometimes kill
the male after
mating, hence
their name
“Black Widow”
Adults reach a maximum size of
half an inch
Shiny, black, globular
abdomen with a
distinctive red
hourglass on the
underside
Their venom contains latrotoxin, a protein which attacks both the nervous
system and the hormones which regulates how the body functions
The vertebrate-specific neurotoxin is α-latrotoxin (α-LTX)
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Selective for vertebrates - ineffective in
insects and crustaceans
High affinity for receptors that are
specific for neuronal and endocrine
cells
Alpha latrotoxin consists of four subunits an α-LTX dimer and δ-LIT dimer
that form a tetramer.
IT IS ONLY TOXIC IN TETRAMERIC FORM
In order to for the tetramer to form
there must be cations such as Ca2+
present.
In its tetrameric form it
interacts with
receptors on the
neuronal membrane
which causes the
insertion of α-LTX into
the membrane, where
the action of the
venom takes place
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This tetramer then binds to membrane
receptors neurexin I, latrophilin 1, and
receptor-like protein tyrosine
phosphatase σ (PTP σ) found on
neuronal membranes of motor cells
and endocrine cells.
Once the tetramer is inserted into the
cell membrane two mechanisms of
actions can occur:
◦ 1. Pore Formation
◦ 2. Receptor-mediated effects
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Pore Formation:
Pores are permeable to Ca2+
Pores are also
permeable to
neurotransmitters,
cations and water
Influx of Ca2+ into
the cell
Stimulates exocytosis
Nerve terminal swelling
This stimulates a massive release of neurotransmitters
resulting in clonic contractions of muscle tissue.
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Receptor-mediated effects:
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α-LTX stimulates a receptor (latrophilin 1-G protein receptor)
Linked to Gαq/11
Induces
release of
Ca2+ from
intracellular
stores
When PLC is activated it
increases cytosolic
concentration of IP3
Increased rate of
spontaneous
exocytosis
Phospholipase C (PLC) is
the downstream effector
of Gαq/11
o Latrophilin with α-LTX can also induce the
activation of Protein Kinase C (PKC).
oPKC is responsible for the phosphorylation of
SNARE proteins.
oThus latrophilin with α-LTX induces the effect of
exocytosis of transport vesicles.
oThis Mechanism is not yet known.
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α-LTX’s ability to form pores in
plasma membrane has been used
to study mammalian nervous
systems.
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Helped confirm the vesicular
hypothesis of transmitter release.
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Establish the requirement of Ca2+
for endocytosis.
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Characterized the existence of
individual neurotransmitter release
sites within central nervous system.
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Mutant form of α-LTX, α-LTXN4C , does not form pores in membrane.
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Stimulation of neuronal receptors by α-LTXN4C mediates release of
intracellular Ca2+ stores.
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Excitatory stimulation caused by intracellular Ca2+ release without
endocytosis of additional Ca2+ indicates two pools of synaptic vesicles:
The readily releasable pool, and the depot pool.
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The Bite (IS THE ONLY WAY FOR THE TOXIN TO BE
ABSORBED VIA THE BLOOD) is similar to a pin prick,
which takes its effect in 30 to 60 minutes which results
in:
◦ Pain in bite are may become generalized
◦ Muscle cramps (especially shoulder and back)
◦ Abdominal pain – may mimic conditions of appendicitis or
gallbladder problems
◦ Chest pain – may be mistaken for a heart attack
◦ Blood Pressure and Heart Rate Elevated
◦ Nausea, vomiting, fainting, dizziness and respiratory
problems may follow
People RARELY die from a black widow's bite.
Life-threatening reactions are generally seen only
in small children and the elderly.
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The victim usually recovers in 2 to 5 days. Only 1% of all black
widow attacks are fatal.
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Despite the low mortality rates it is still recommended that one
immediately see a Doctor after an bite.
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Calcium gluconate (anti-venom) can also be administered by an
physician
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The wound should also be cleansed and Ice Packs can be used
for the pain
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The LD50 of α-LTX measured in μg/kg:
◦ Guinea Pig: 0.1
◦ Pigeon: 0.4
◦ Mouse: 0.9
◦ Chicken: 2.1
Human LD50 ranges from 4.3 to 20 to 95 μg/kg
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Find spider
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Milk spider
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Purify venom
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Inject pure venom into horse or sheep
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Animal makes antibodies against venom
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Withdraw blood and separate antibodies
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Concentrate antibodies into a solution
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Inject into blood of recently bitten victim
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Indigenous South Americans have traditionally used the venom as
an Aphrodisiac
Chilean scientists are working on a peptide derived from the venom
to produce a Male Contraceptive Agent (Romero et. al., 2011)
The venom Counters The Effects Of innvervation of muscles
paralyzed by Botulinum Toxin (Gomez et. al., 1981)
A particular peptide with a building block of proteins could help
Treat Alzheimer's’
Could be First Documented Death from α-LTX
No deaths
have been
reported in the
past 10 years
in the U.S.
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Daniela Holmqvist, a rookie from Sweden on the Ladies
European Tour was bitten by a spider during a round in
Canberra, Australia.
Most recent case of α-LTX in humans
February 14, 2013
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Black Widow spiders, Latrodectus mactans, are ubiquitous in nearly all
regions.
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Black Widow venom is a tetramer polypeptide that is injected into the
spiders prey.
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Once in the bloodstream α-LTX binds to neuronal and endocrine cell
membranes, inducing pore formation and Ca2+ uptake, which in turn
causes vesicular neurotransmitter exocytosis. This produces clinical
symptoms such as muscle pain, tachycardia, diaphoresis, and in
extreme cases death.
Most Black Widow envenomation's do not result in long term health
problems, and death is rare .
α-LTX has been used to research neuronal cell function, and uses for
Black Widow venom as a therapeutic agent for several conditions are
being investigated.
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