Maize leaf phosphoenolpyruvate carboxylase: phosphorylation of Ser15 with a mammalian cyclic AMP-dependent protein kinase diminishes sensitivity to inhibition by malate

AbstractThe so-called light-activation of phosphoenolpyruvate carboxylase (PEPC) (EC 4.1.1.31) involved in C4 photosynthesis is known to be mediated by phosphorylation. A cyclic AMP-dependent protein kinase from bovine heart was found to be able to phosphorylate PEPC. The phosphorylation was accompanied by the changes in kinetic properties, which were very similar to the reported light activation. The phosphorylated amino acid residue was identified as Ser and the position of this Ser on the primary structure [(1988) FEBS Lett. 229, 107-110] was determined to be Ser15

Upregulation of ANGPTL6 in mouse keratinocytes enhances susceptibility to psoriasis

Psoriasis is a chronic inflammatory skin disease marked by aberrant tissue repair. Mutant mice modeling psoriasis skin characteristics have provided useful information relevant to molecular mechanisms and could serve to evaluate therapeutic strategies. Here, we found that epidermal ANGPTL6 expression was markedly induced during tissue repair in mice. Analysis of mice overexpressing ANGPTL6 in keratinocytes (K14-Angptl6 Tg mice) revealed that epidermal ANGPTL6 activity promotes aberrant epidermal barrier function due to hyperproliferation of prematurely differentiated keratinocytes. Moreover, skin tissues of K14-Angptl6 Tg mice showed aberrantly activated skin tissue inflammation seen in psoriasis. Levels of the proteins S100A9, recently proposed as therapeutic targets for psoriasis, also increased in skin tissue of K14-Angptl6 Tg mice, but psoriasis-like inflammatory phenotypes in those mice were not rescued by S100A9 deletion. This finding suggests that decreasing S100A9 levels may not ameliorate all cases of psoriasis and that diverse mechanisms underlie the condition. Finally, we observed enhanced levels of epidermal ANGPTL6 in tissue specimens from some psoriasis patients. We conclude that the K14-Angptl6 Tg mouse is useful to investigate psoriasis pathogenesis and for preclinical testing of new therapeutics. Our study also suggests that ANGPTL6 activation in keratinocytes enhances psoriasis susceptibility