physiology of mucin

7/31/2019 Physiology of Mucin

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PHYSIOLOGY OF MUCIN

SUBMITTED TO: SUBMITTED BY:MRS. VANDANA CHAUDHARY NITIN


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CONTENTS

INTRODUCTION

GENES OF MUCIN

PROTEIN STRUCTURE

GLYCOSYLATION AND AGGREGATION

SECRETION

CLINICAL SIGNIFICANCE

CONCLUSION

REFERENCES


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INTRODUCTION

High molecular weight , heavily glycosylated proteins ( glyco-conjugates )

Produced by epithelial tissues in most metazoans

Ability to form gels; therefore secretions, serving functions fromlubrication to cell signalling to forming chemical barriers,inhibitory role

Overexpression of the mucin proteins, especially MUC1 is associated with many types of cancer.
http://en.wikipedia.org/wiki/Molecular_weighthttp://en.wikipedia.org/wiki/Glycosylationhttp://en.wikipedia.org/wiki/Proteinshttp://en.wikipedia.org/wiki/Glycoconjugatehttp://en.wikipedia.org/wiki/Glycoconjugatehttp://en.wikipedia.org/wiki/MUC1http://en.wikipedia.org/wiki/MUC1http://en.wikipedia.org/wiki/MUC1http://en.wikipedia.org/wiki/Glycoconjugatehttp://en.wikipedia.org/wiki/Glycoconjugatehttp://en.wikipedia.org/wiki/Glycoconjugatehttp://en.wikipedia.org/wiki/Proteinshttp://en.wikipedia.org/wiki/Glycosylationhttp://en.wikipedia.org/wiki/Molecular_weighthttp://en.wikipedia.org/wiki/Molecular_weighthttp://en.wikipedia.org/wiki/Molecular_weight


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GENES OF MUCIN

At least 19 human mucin genes have been distinguished by cDNA cloning MUC1 , MUC2, MUC3A , MUC3B, MUC4, MUC5AC ,MUC5B , MUC6 , MUC7 , MUC8, MUC12, MUC13, MUC15,MUC16 , MUC17 , MUC19, and MUC20 .

The major secreted airway mucins are MUC5AC and MUC5B ,

while MUC2 is secreted mostly in the intestine but also in the airway.
http://en.wikipedia.org/wiki/MUC1http://en.wikipedia.org/wiki/MUC2http://en.wikipedia.org/wiki/MUC3Ahttp://en.wikipedia.org/wiki/MUC4http://en.wikipedia.org/wiki/MUC5AChttp://en.wikipedia.org/wiki/MUC5Bhttp://en.wikipedia.org/wiki/MUC6http://en.wikipedia.org/wiki/MUC7http://en.wikipedia.org/wiki/MUC16http://en.wikipedia.org/wiki/MUC17http://en.wikipedia.org/wiki/MUC20http://en.wikipedia.org/wiki/MUC5AChttp://en.wikipedia.org/wiki/MUC5Bhttp://en.wikipedia.org/wiki/MUC2http://en.wikipedia.org/wiki/MUC2http://en.wikipedia.org/wiki/MUC2http://en.wikipedia.org/wiki/MUC5Bhttp://en.wikipedia.org/wiki/MUC5Bhttp://en.wikipedia.org/wiki/MUC5Bhttp://en.wikipedia.org/wiki/MUC5AChttp://en.wikipedia.org/wiki/MUC5AChttp://en.wikipedia.org/wiki/MUC5AChttp://en.wikipedia.org/wiki/MUC20http://en.wikipedia.org/wiki/MUC20http://en.wikipedia.org/wiki/MUC17http://en.wikipedia.org/wiki/MUC17http://en.wikipedia.org/wiki/MUC16http://en.wikipedia.org/wiki/MUC16http://en.wikipedia.org/wiki/MUC7http://en.wikipedia.org/wiki/MUC7http://en.wikipedia.org/wiki/MUC6http://en.wikipedia.org/wiki/MUC6http://en.wikipedia.org/wiki/MUC5Bhttp://en.wikipedia.org/wiki/MUC5Bhttp://en.wikipedia.org/wiki/MUC5Bhttp://en.wikipedia.org/wiki/MUC5AChttp://en.wikipedia.org/wiki/MUC5AChttp://en.wikipedia.org/wiki/MUC5AChttp://en.wikipedia.org/wiki/MUC4http://en.wikipedia.org/wiki/MUC4http://en.wikipedia.org/wiki/MUC3Ahttp://en.wikipedia.org/wiki/MUC3Ahttp://en.wikipedia.org/wiki/MUC3Ahttp://en.wikipedia.org/wiki/MUC2http://en.wikipedia.org/wiki/MUC2http://en.wikipedia.org/wiki/MUC1http://en.wikipedia.org/wiki/MUC1


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PROTEIN STRUCTURE

composed of two distinct regions

The amino- and carboxy-terminal (lightly glycosylated, but

rich in cysteines which participate in establishing disulfide bonds).

A large central region of multiple repeats of 10 to 80residue sequences in which up to half are serine or threonine .
http://en.wikipedia.org/wiki/Cysteinehttp://en.wikipedia.org/wiki/Disulfidehttp://en.wikipedia.org/wiki/Serinehttp://en.wikipedia.org/wiki/Threoninehttp://en.wikipedia.org/wiki/Threoninehttp://en.wikipedia.org/wiki/Serinehttp://en.wikipedia.org/wiki/Disulfidehttp://en.wikipedia.org/wiki/Cysteine


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Glycosylation And Aggregation

Mucin genes encode mucin monomers that are synthesized as rod-shape apomucin cores that are post-translationally modified by exceptionally abundant glycosylation .

The dense "sugar coating" of mucins gives them considerable water-

holding capacity and also makes them resistant to proteolysis , which may be important in maintaining mucosal barriers.

Mucins are secreted as massive aggregates of proteins with molecular masses of roughly 1 to 10 million Da. Within these

aggregates, monomers are linked to one another mostly by non-covalent interactions, although intermolecular disulfide bonds may also play a role in this process.
http://en.wikipedia.org/wiki/Genehttp://en.wikipedia.org/wiki/Monomershttp://en.wikipedia.org/w/index.php?title=Apomucin&action=edit&redlink=1http://en.wikipedia.org/wiki/Glycosylationhttp://en.wikipedia.org/wiki/Hygroscopichttp://en.wikipedia.org/wiki/Hygroscopichttp://en.wikipedia.org/wiki/Proteolysishttp://en.wikipedia.org/wiki/Mucous_membranehttp://en.wikipedia.org/wiki/Monomerhttp://en.wikipedia.org/wiki/Covalenthttp://en.wikipedia.org/wiki/Disulfidehttp://en.wikipedia.org/wiki/Disulfidehttp://en.wikipedia.org/wiki/Covalenthttp://en.wikipedia.org/wiki/Monomerhttp://en.wikipedia.org/wiki/Mucous_membranehttp://en.wikipedia.org/wiki/Proteolysishttp://en.wikipedia.org/wiki/Hygroscopichttp://en.wikipedia.org/wiki/Hygroscopichttp://en.wikipedia.org/wiki/Hygroscopichttp://en.wikipedia.org/wiki/Glycosylationhttp://en.wikipedia.org/w/index.php?title=Apomucin&action=edit&redlink=1http://en.wikipedia.org/wiki/Monomershttp://en.wikipedia.org/wiki/Gene


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SECRETION

Upon stimulation

MARCKS (myristylated alanine-rich C kinase substrate) coordinates secretion from mucin filled vesicles .

Fusion of the vesicles to the plasma membrane causes release of the mucin, which as it exchanges Ca 2+ for Na + expands up to 600 fold.

The result is a viscoelastic product of interwoven molecules which, combined with other secretions is called Mucin.
http://en.wikipedia.org/wiki/Vesicle_(biology)http://en.wikipedia.org/wiki/Plasma_membranehttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Viscoelastichttp://en.wikipedia.org/wiki/Viscoelastichttp://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Plasma_membranehttp://en.wikipedia.org/wiki/Plasma_membranehttp://en.wikipedia.org/wiki/Plasma_membranehttp://en.wikipedia.org/wiki/Vesicle_(biology)


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CLINICAL SIGNIFICANCE

Increased mucin production occurs in many adenocarcinomas , including cancersof the pancreas, lung, breast, ovary, colon and other tissues.

overexpressed in lung diseases such as asthma , bronchitis , COPD or cysticfibrosis .

MUC1 and MUC4 have been extensively studied in relation to their pathologicalimplication in the disease process.

Mucins are under investigation as possible diagnostic markers for malignanciesand other disease processes in which they are most commonly over- or mis-expressed.

Abnormal deposits of mucin are responsible for the non-pitting facial edemaseen in untreated hypothyroidism.
http://en.wikipedia.org/wiki/Adenocarcinomahttp://en.wikipedia.org/wiki/Asthmahttp://en.wikipedia.org/wiki/Bronchitishttp://en.wikipedia.org/wiki/Chronic_obstructive_pulmonary_diseasehttp://en.wikipedia.org/wiki/Cystic_fibrosishttp://en.wikipedia.org/wiki/Cystic_fibrosishttp://en.wikipedia.org/wiki/Cystic_fibrosishttp://en.wikipedia.org/wiki/Cystic_fibrosishttp://en.wikipedia.org/wiki/Cystic_fibrosishttp://en.wikipedia.org/wiki/Chronic_obstructive_pulmonary_diseasehttp://en.wikipedia.org/wiki/Bronchitishttp://en.wikipedia.org/wiki/Asthmahttp://en.wikipedia.org/wiki/Adenocarcinoma


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CONCLUSION

The picture that emerges is that of a macromolecule with a complex organization into domains with different structures.From the polymeric view point mucin can be considered as a multi block copolymer with alternating poly electrolytic domains having a grafted sugar brush, connected by flexible

regions with less glycosylation and the tendency to formpolymers. The molecule has both hydrophobic and hydrophilic regions with the ability to form H-bonds, and electrostatic interactions. This wide range of interactions causes it to

aggregate gel and form mucoadhesive interactions with other substances. These physical properties are of direct relevance to the physiological functions of mucus in normal and diseased states. An understanding these properties is of considerable current interest because of the many biomedical applications.


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REFERENCES

Bansil R, Stanley E, LaMont JT: Mucin biophysics. Ann Rev Physiol 57:635, 1995.

Gendler SJ, Spicer AP: Epithelial mucin genes. Ann Rev

Physiology 57:607, 1995.

Tabak LA: In defense of the oral cavity: Structure, biosynthesis and function of salivary mucins. Ann Rev Physiology 57:547,1995.

http:// en.wikipedia.org/wiki/Mucin
http://en.wikipedia.org/wiki/Mucinhttp://en.wikipedia.org/wiki/Mucinhttp://en.wikipedia.org/wiki/Mucinhttp://en.wikipedia.org/wiki/Mucin

physiology of mucin

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