Purification of the keratan sulfate proteoglycan expressed in prostatic secretory cells and its identification as lumican.
BACKGROUND
Secretory epithelial cells of human prostate contain a keratan sulfate proteoglycan (KSPG) associated with the prostatic secretory granules (PSGs). The proteoglycan has not been identified, but like the PSGs, it is lost in the early stages of malignant transformation.


METHODS
Anion exchange and affinity chromatography were used to purify KSPG from human prostate tissue. Enzymatic deglycosylation was used to remove keratan sulfate (KS). The core protein was isolated using 2D gel electrophoresis, digested in-gel with trypsin, and identified by peptide mass fingerprinting (PMF).


RESULTS
The purified proteoglycan was detected as a broad smear on Western blots with an apparent molecular weight of 65-95 kDa. The KS moiety was susceptible to digestion with keratanase II and peptide N-glycosidase F defining it as highly sulfated and N-linked to the core protein. The core protein was identified, following deglycosylation and PMF, as lumican and subsequently confirmed by Western blotting using an anti-lumican antibody.


CONCLUSIONS
The KSPG associated with PSGs in normal prostate epithelium is lumican. While the role of lumican in extracellular matrix is well established, its function in the prostate secretory process is not known. It's potential to facilitate packaging of polyamines in PSGs, to act as a tumor suppressor and to mark the early stages of malignant transformation warrant further investigation.
Holland
John W
JW
Institute for Molecular Bioscience, University of Queensland, Brisbane, Australia. j.holland@imb.uq.edu.au
Meehan
Katie L
KL
Redmond
Sharon L
SL
Dawkins
Hugh J S
HJ
D000595:Amino Acid Sequence; D015153:Blotting, Western; D011508:Chondroitin Sulfate Proteoglycans / Q000032:analysis* / Q000096:biosynthesis*; D002846:Chromatography, Affinity; D015180:Electrophoresis, Gel, Two-Dimensional; D006801:Humans; D007632:Keratan Sulfate / Q000032:analysis* / Q000096:biosynthesis*; D000071234:Lumican; D008297:Male; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D011467:Prostate / Q000737:chemistry*
D011508:Chondroitin Sulfate Proteoglycans; C000604306:LUM protein, human; D000071234:Lumican; D007632:Keratan Sulfate