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vitreous. It has been demonstrated that processing of CGs is tissue- and cell-specific
(Yoshida et al. 2009 ). The numerous cleavage sites are consistent with the specific-
ity of prohormone convertases (PC1/3 and PC2) and carboxypeptidase E (CPE),
that reside within chromaffin granules (Metz-Boutigue et al. 1993 ; Seidah and
Chrétien 1999 ). In addition, cathepsin L (Biswas et al. 2009 ), carboxypeptidases,
aminopeptidases (Hook et al. 1982 ), and trypsin-like proteases (Evangelista et al.
1982 ) are also involved in the proteolytic processing of CGA. These are typically
regulated by endogenous protease inhibitors such as endopins 1 and 2, which pos-
sess high homology to alpha 1 antitrypsin A1AT (Hook and Metz-Boutigue 2002 ).
The discovery that pancreastatin, a CGA-derived peptide inhibits insulin secre-
tion from pancreatic beta-cells, initiated the concept of prohormone (Eiden 1987 ;
Nakano et al. 1989 ). The release of these CGs-derived peptides from chromaffin
cells results from the nicotinic cholinergic stimulation and regulates several neuro-
endocrine functions (Helle and Serck-Hanssen 1975 ).
The natural processing of CGA in PMNs after stimulation by the leukocidin
Panton-Valentin (Lugardon et al. 2000 ; Briolat et al. 2005 ) generates a range of
CGA-derived fragments containing VS-I and catestatin CAT. Wherever PMNs
accumulate in response to invading microorganisms, tissue inflammation, and sites
of mechanical injury, these released peptides may affect a wide range of cells
involved in inflammatory responses, e.g. endothelial, endocardial and epithelial
cells, other leucocytes, fibroblasts, cardiomyocytes, and vascular and intestinal
smooth muscle.
Furthermore, Leukotoxins E/D (LukE/D) from Staphylococcus aureus were also
used to induce PMNs secretions. Full-length CGA (1–439) and several CGA-
derived fragments were identified including CGA1−291, CgA1−249, CgA1− 209
and CgA1−115 (Aslam et al. 2013a).
CGA-immunoreactive fractions were also detected in rat heart extracts (Glattard
et al. 2006 ) by using western blot and TOF/TOF mass spectrometry. Four endoge-
nous N-terminal CGA-derived peptides containing the vasostatin sequence were
characterized as CGA4-113, CGA1-124, CGA1-135 and CGA1-199. Post-
translational modifications of these fragments were identified: phosphorylation at
S96 and O-glycosylation (trisaccharide, NAcGal-Gal-NeuAc) at T126. This first
identification of CGA-derived peptides containing the VS-I motif in rat heart sup-
ports their role in cardiac physiology by an autocrine/paracrine mechanism.
We evaluated the presence and processing of CGA in the vitreous of diabetic
patients (DV) compared with non-diabetic vitreous (NDV) (Fournier et al. 2011 )
because inflammation has been linked to the development of diabetic retinopathy.
ELISA, Western blot, RP-HPLC, dot blot, protein sequencing and mass spectrometry
were used to study the quantitative expression and the processing of CGA. Expression
was higher in DV than in NDV. Mean concentration of CGA evaluated by ELISA was
90.8 ng/L (±90.1) in DV vs. 29.7 ng/L (±20.9) in NDV (p = 0.039). In DV, proteomic
analyses showed that long CGA-derived fragments and A1AT were overexpressed,
suggesting possible inhibition of the proteolytic process. In DV, the increase of the
presence of complete CGA and the attenuation of its endogenous proteolytic process-
ing could participate in diabetic retinopathy progression by reducing the presence of
M.-H. Metz-Boutigue and F. Schneider