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Protein tyrosine phosphatases (PTPs) are regulators of growth factor signalling in vascular remodelling. The aim of this study was to evaluate PTP expression in the context of PDGF-signalling in the adventitia after angioplasty. Utilising a rat carotid artery model, the adventitial layers of injured and non-injured vessels were laser microdissected. The mRNA expression of the PDGF beta-receptor, the ligands PDGF-A/B/C/D and the receptor-antagonising PTPs (DEP-1, TC-PTP, SHP-2, PTP1B) were determined and correlated to vascular morphometrics, proliferation markers and PDGF beta-receptor phosphorylation. The levels of the PDGF beta-receptor, PDGF-C and PDGF-D were upregulated concurrently with the antagonising PTPs DEP-1 and TC-PTP at day 8, and normalised at day 14 after vessel injury. Although the proliferation parameters were time-dependently altered in the adventitial layer, the phosphorylation of the PDGF beta-receptor remained unchanged. The expression dynamics of specific PTPs indicate a regulatory role of PDGF-signalling also in the adventitia during vascular remodelling.

The recent finding of peptide:N-glycanase (PNGase) in medaka embryos (Seko, A., Kitajima, K., Inoue, Y., & Inoue, S., J.Biol. Chem. 266, 22110 (1991)) raised the question of how widespread is the occurrence of this type of de-N-glycosylating enzyme. In experiments designed to identify PNGase in the mammalian system, we searched for its activity in some cultured cell lines. Incubation of a 14C-labeled N-glycopeptide with extracts prepared from cultured cells resulted in producing the free glycan and the peptide. Detailed characterizations of the products, formed upon incubation of a 14C-labeled N-glycopeptide substrate with the enzyme preparation from C3H mouse loose connective tissue-derived L-929 cells, by HPLC, amino acid and carbohydrate composition analyses, and peptide sequence analysis unequivocally established the reaction products to be the free glycan having di-N-acetylchitobiosyl sequence at its reducing end and free peptide in which the originally glycan-linked Asn residue was converted to the Asp residue. This represents the first demonstration of PNGase in mammalian cells and thus PNGase appears to be a very common enzyme expressed in not only plants and bacteria but also a wide range of animals although its functional significance remains to be clarified.

Dog, monkey and human aortic tissues contained two distinct types of angiotensin II-generating enzymes; angiotensin converting enzyme (ACE) and chymostatin-sensitive angiotensin II-generating enzyme (CAGE). Endothelium, media and adventitia of canine thoracic aortae were separated using collagenase digestion, and determined for their ACE and CAGE activity. ACE activity was assayed by hippuryl-His-Leu cleavage. CAGE activity was estimated with ANG I as substrate in the presence of inhibitors of ACE and angiotensinases. His-Leu, the common product of both enzyme reactions, was fluorimetrically quantified after o-phthalaldehyde condensation. ACE localized mainly in endothelium, while CAGE distributed predominantly in adventitia. Similar results were obtained with human and monkey aortae. Such a contrasting distribution may indicate the distinct functional role of these two enzymes.