Elevated dosage of the GAC1 gene from the yeast Saccharomyces cerevisiae causes hyperaccumulation of glycogen whereas a gene disruption of GAC1 results in reduced glycogen levels. Glycogen synthase is almost entirely in the active, glucose 6‐phosphate‐independent, form in cells with increased gene dosage of GAC1 whereas the enzyme is mostly in the inactive form in strains lacking GAC1. GAC1 encodes an 88 kDa protein that is similar to the regulatory subunit (RG1) of phosphoprotein phosphatase type 1 (PP‐1) from skeletal muscle that targets PP‐1 to glycogen particles. Taken together, these results suggest that GAC1 encodes a regulatory subunit of PP‐1. As previously shown for glycogen phosphorylase (GPH1), GAC1 RNA accumulates concomitantly with the appearance of glycogen. A strain with a mutation in the regulatory subunit of the cAMP‐dependent protein kinase (bcy1) fails to accumulate GPH1 and GAC1 RNA. These results point to coordinate regulation of enzymes involved in glycogen metabolism at the level of RNA accumulation and indicate that at least part of this control is exerted by the RAS‐cAMP pathway.

SUMMARY:In an attempt to define the roles of prostaglandin H synthase 1 (PGHS-1, cyclooxygenase-1, COX-1) and prostaglandin H synthase 2 (PGHS-2, cyclooxygenase-2, COX-2) in wound healing, we investigated the healing of incisional dermal wounds in wild-type, PGHS-1 null, and PGHS-2 null mice. We measured tensile strength of the wounds, levels of PGHS-1 and PGHS-2 mRNA in the wound site, and histologic markers for the inflammatory, proliferative, and remodeling phases of wound healing. Although no gross visible differences were noted among healed wounds of the different mouse types, measurement of tensile strength showed that both PGHS-1 and PGHS-2 null wounds were weaker (75% and 70%, respectively) than wild-type wounds at 12 days after incision. At Day 8 the endothelial staining was 70% greater in the wounds of PGHS-2 null mice compared with their wild-type counterparts. In contrast at Day 12, staining for macrophages and myofibroblasts was less in PGHS-1 null wounds compared with wild-type and PGHS-2 null tissue. Compensatory expression of the alternate PGHS mRNA could be demonstrated by RT-PCR in the wounds of PGHS null mice on Days 1 and 4. We conclude that both PGHS-1 and PGHS-2 genes play distinct roles in the process of dermal wound healing. (Lab Invest 2002, 82:919 -927).

Mice lacking a functional cyclooxygenase-2 (COX-2) gene develop abnormal kidneys that contain hypoplastic glomeruli and reduced proximal tubular mass, and they often die of renal failure. A comparison of kidney-specific gene expression between wild-type and COX-2-deficient mice by cDNA microarrays revealed that although more than 500 mRNAs were differentially expressed between the two strains of mice depending on their ages, the genes encoding pre-pro-epidermal growth factor (pre-pro-EGF) and Tamm-Horsfall protein (THP)/uromodulin were aberrantly expressed in the kidneys of COX-2 -/- mice at all stages of their development. Downregulation of EGF could potentially affect renal development, and THP/uromodulin gene has been implicated in abnormal kidney development and end-stage renal failure in humans. We assessed in detail mechanism of defective THP/uromodulin gene expression and its potential consequences in COX-2-deficient mice. Consistent with the microarray data, the steady-state levels of THP/uromodulin mRNA were severely reduced in the COX-2 -/- kidney. Furthermore, reduced expression of renal THP/uromodulin, as assessed by Western blot and immunohistological methods, was closely corroborated by a corresponding decline in the urinary secretion of THP/uromodulin in COX-2 -/- mice. Finally, we demonstrate that the bladders of COX-2 -/- mice, in contrast to those of the wild-type mice, are highly susceptible to colonization by uropathogenic Escherichia coli.

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We have isolated a snf1/ccr1 mutant of Saccharomyces cerevisiae which loses viability upon starvation and fails to accumulate glycogen in response to abrupt depletion of phosphate or glucose. A snf1 null mutant is sensitive to heat stress and starvation and fails to accumulate glycogen during growth in rich medium. The phenotypes of the snf1 mutants are those commonly associated with an overactivation of the adenylate cyclase pathway. Mutations in adenylate cyclase or RAS2 which decrease the level of cAMP in the cell moderate the snf1 phenotype. In contrast, a mutation in RAS2 (RAS2val19) which increases the level of cAMP or a mutation in the regulatory subunit (BCY1) of cAMP-dependent protein kinase which results in unregulated cAMP-dependent protein kinase activity accentuates the snf1 phenotype. However, the action of SNF1 in the stress response appears at least partly independent of cAMP-dependent protein kinase because a snf1 phenotype is observed in a strain that lacks all three of the genes that encode the catalytic subunits of cAMP-dependent protein kinase. SNF1 therefore acts at least in part through a cAMP-independent pathway.