Soluble glycoproteins of the lacrimal sac: role in defense with special reference to prolactin-inducible protein (PIP)

ABSTRACT

Purpose: Glycoproteins play an important role in human mucosal defenses and immunity-related cell-to-cell interactions. The aim of the present study is to investigate the presence and patterns of lacrimal sac glycoproteins involved in defense mechanisms with a special reference to prolactin-inducible protein (PIP).

Methods: The study was performed on healthy lacrimal sacs obtained from exenteration samples immediately after surgery and frozen at −80 degrees for subsequent analysis. Four lectins namely Concanavalin A (Con A), Dolichos lablab lectin (DLL), Wheat Germ agglutinin (WGA), and Momordica charantia lectin (MCL) were purified by affinity chromatography. Soluble proteins extract of the lacrimal sac was subjected to chromatography on lectin-affigel columns. Eluted samples from each of the lectin coupled-affigels were analyzed by 10% SDS-PAGE under reducing conditions and the protein bands were visualized using Coomassie blue stain. The protein gel bands were further subjected to mass spectrometry for glycoprotein analysis.

Results: Mass spectrometry identified several glycoproteins from the lacrimal sac extracts, with known roles in defense mechanisms. The number of such glycoproteins identified were 9 each from Con A and DLL-I affinity eluted gel bands and 8 and 14 from MCL and WGA affinity eluted gel bands, respectively. Interestingly, PIP was detected in significant proportions in all the eluted gel bands with WGA showing the highest expression.

Conclusions: This study is the first step towards the lacrimal sac glycoprotein profiling. PIP could be a major lead for further work on the etiopathogenesis of lacrimal drainage obstructions.

KEYWORDS:

• Lacrimal sac
• glycoproteins
• prolactin-inducible protein
• lectins
• PANDO

Acknowledgments

The authors thank Dr. B. Raman, CCMB Proteomics facility for his help in recording Mass spectra. The authors thank the UGC-SAP-DRS-1 and DST-FIST support for the Biochemistry Department.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Mohammad Javed Ali receives royalties from Springer for the textbook ‘Principles and Practice of Lacrimal Surgery’ and treatise ‘Atlas of Lacrimal Drainage Disorders’ and is a registered PhD student at the University of Hyderabad. This manuscript is in part result of his PhD work.