5302 salivary proteins

8/14/2019 5302 Salivary Proteins

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Salivary Proteins

DENT 5302

Topics in Dental BiochemistryDr. Joel Rudney


2/17

Clinical Importance Demographic change - the number of elderly will increase

Implications:

Increases in diseases affecting salivary glands

Sjogren's syndrome, other autoimmune diseases,

Head and neck cancer (radiation therapy)

Increased use of medications with effects on saliva

Anticholinergic (antihistamines, antidepressants)

Reduced flow - indirect/direct effects on proteins

Beta adrenergic agonists and antagonists

Direct effects on protein synthesis/secretion

(asthma, hypertension, cardiovascular disease)


3/17

Salivary protein therapies

Current artificial salivas replace mainly fluids, ions

Genetically-engineered human salivary proteins soon

Raised from seed

Which ones go in artificial saliva? How much to add?

Already toothpastes/rinses containing saliva proteins

Biotne (peroxidase, lysozyme lactoferrin)

Histatin rinses/gels in trials

Clinicians will need to be able to evaluate new products


4/17

Origins of salivary proteins

Different secretory cells in different glands

Serous acinar - water, ions, proteins

Most in parotid, less in SM/SL

Mucus acinar - complex glycoproteins

Only SM/SL and minor glands

Different proteins emphasized in different glands

Duct cells also secrete proteins - differs among glands

Immune system cells contribute proteins

B cell product (S-IgA) translocated into ducts

Neutrophils - indirect leakage into gingival crevice

Leakage from gingival fluid contributes serum proteins (WS only)

Oral epithelial cells release surface proteins (whole saliva only)


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Functions - Protect tissues

Protect oral surfaces by forming pellicle

Statherin, acidic proline-rich proteins, amylase, histatins,

cystatins, MUC7 mucin, lysozyme, albumin

Lubrication - oral surfaces must slide freely

Statherin, MUC5B mucin (also reflux protection)

Maintain saliva calcium in equilibrium with enamel

Saliva supersaturated with calcium and phosphate

Precipitation must be prevented

Statherin, aPRP, histatins, cystatins


6/17

Functions - Food processing

Initial breakdown of starches - Amylase

Binding/detoxification of dietary tannins

aPRP, basic PRP, histatins

Protein processing - Kallikrein and other proteases

Swallowing - MUC5B


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Functions - Manage Microbes

Antimicrobial functions (bacteria, fungi, viruses)

Direct - cell killing - Histatins, lysozyme, amylase, MUC7,

lactoferrin, defensins, peroxidase

Indirect - Inhibition of infectivity, microbial metabolism,

bacterial/viral proteases - Lactoferrin, cystatins, histatins,basic

PRP, SLIPI, peroxidase, S-IgA

"Aggregation" - bind to microbes, clear by swallowing - MUC7,

lysozyme, lactoferrin, glcosylated PRP, parotid agglutinin, extra-

parotid glycoprotein, S-IgA


8/17

Functions - Microbes Manage

Microbial use of saliva proteins (coevolution)

Microbial adherence to pellicle proteins - Statherin, aPRP,

amylase, MUC5B, MUC7,lysozyme, lactoferrin, glcosylatedPRP, parotid agglutinin, extra-parotid glycoprotein, S-IgA,

peroxidase

Microbial metabolism of salivary proteins - MUC5B

Microbial use to metabolize host diet - Amylase


9/17

Complexity and Redundancy

Most saliva proteins have more than one function

Different domains on the same protein for different functions

Most saliva proteins cans be "amphifunctional

Some actions help host, others seem to help microbes

Also can be mediated by different domains

Many proteins share similar functions - redundancy

Multiple gene families

2-4 closely linked genes coding very similar proteins

aPRP, bPRP, gPRP, cystatins, histatins ,amylase, MUCs

Multiple alleles for each gene

Unrelated proteins with the same function - backup systems?


10/17

Fragments and Complexes

Many salivary proteins are cleaved by proteases

During secretion or in the mouth

aPRP, bPRP, gPRP, histatins,S-IgA

Fragments may function differently than intact proteins

Proteins function differently together than they do alone

Lysozyme, lactoferrin, peroxidase

Salivary proteins bind in large heterotypic complexes

MUC5B, amylase, aPRP, S-IgA, peroxidase, lysozyme,

lactoferrin, statherin

Complexes function differently than component proteins


11/17

Pictures of proteins in pellicle

Schupbach et. al. 2001, Eur J Oral Sci 109:60

histatinsaPRP statherin


12/17

Pictures of proteins in pellicle

Schupbach et. al. 2001, Eur J Oral Sci 109:60

statherin histatins


13/17

Statherin up close

Multiple gene family

Small tyrosine-rich phosphoproteins

Negatively charged Ca2+ binding N-terminal

Two phosphoserines - additional negative charges

Maintains Ca2+ balance, strongly prevents precipitation

Binds tooth surfaces and changes conformation

C-terminal rich in "bulky" tyrosines

Lubrication of tooth surfaces (pellicle)

Adherence ofActinomyces species (pellicle)


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Acidic PRP up close

Multiple gene family

Proline-rich phosphoproteins

Negatively charged Ca2+ binding N-terminal

Two phosphoserines - additional negative charges

Ca2+ balance, strongly prevents precipitation

Binds tooth surfaces and changes conformation

C-terminal rich in "bulky" prolines

Adherence ofStreptococcus species (pellicle)

Proteases cleave N-terminal from C-terminal

Free C-terminal binds tannins; blocks bacterial adhesion


15/17

Histatins up close

Multigene family - largest is phosphoprotein, others not

Small peptides after proteolysis

Positive charge - histidine-rich

Microbial cell damage - antibacterial and anti-fungal

Also Ca2+ balance, tannin binding, protease inhibitor

Clinical interest - very safe - easy to make

Early trials with histatin rinses and gels

Some benefit in experimental gingivitis model

No oral hygiene for a month

No trials with caries, periodontitis, or candidiasis patients yet


16/17

Current Products

Products with added lysozyme, lactoferrin, peroxidase

All influence aggregation/adherence, plus unique effects

Px enzyme - bacterial H2O2 + saliva SCN- > OSCN-

OSCN- inhibits/kills bacteria

Removing H2O2 may protect soft tissues

Lz enzyme cleaves bacterial cell walls > lysis

Also positive charge effects similar to histatins

Lfsequesters iron from some microbes, but not all

Unsaturated Lf is independently bactericidal

Clinical interest - can be purified from cow's milk

Biotne toothpaste, rinses, gum, dry mouth gels

Minor to minimal benefit in published clinical trials


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Future Prospects

Ideas about salivary protein function come from lab

Experimental models are greatly simplified

Change only one factor at a time

The mouth is an extremely complex environment

Difficult to isolate effects of single proteins

Redundancy may dilute the effects of supplements

We need to understand how different proteins work together

Supplements may need to be in the form of protein complexes

5302 salivary proteins

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