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Biomedical subjects

J Cryan

Publications and source records attributed to J Cryan.

8 recordsLinked to original sources
PubMed1996

T cell responses in calcineurin A alpha-deficient mice.

We have created embryonic stem (ES) cells and mice lacking the predominant isoform (alpha) of the calcineurin A subunit (CNA alpha) to study the role of this serine/threonine phosphatase in the immune system. T and B cell maturation appeared to be normal in CNA alpha -/- mice. CNA alpha -/- T cells responded normally to mitogenic stimulation (i.e., PMA plus ionomycin, concanavalin A, and anti-CD3 epsilon antibody). However, CNA alpha -/- mice generated defective antigen-specific T cell responses in vivo. Mice produced from CNA alpha -/- ES cells injected into RAG-2-deficient blastocysts had a similar defective T cell response, indicating that CNA alpha is required for T cell function per se, rather than for an activity of other cell types involved in the immune response. CNA alpha -/- T cells remained sensitive to both cyclosporin A and FK506, suggesting that CNA beta or another CNA-like molecule can mediate the action of these immunosuppressive drugs. CNA alpha -/- mice provide an animal model for dissecting the physiologic functions of calcineurin as well as the effects of FK506 and CsA.

Animals↗
PubMed1996

Decrease in fat oxidation following a meal in weight-reduced individuals: a possible mechanism for weight recidivism.

This study examined the effect that dietary-induced weight loss has on body composition, energy metabolism, and substrate oxidation at rest and during the 5-hour period following a meal. Twenty older (age:mean +/- SE, 61 +/- 1 years; range, 56 to 70 y) obese (body mass index > 32 kg/m2) subjects (12 women, eight men) completed an 11-week dietary restriction program in which they lost 9 +/- l kg. Fat and fat-free mass were reduced (P < .05) by 15% and 5%, respectively. Resting metabolic rate decreased by 15% (P < .05). Overall, weight loss did not alter the percentage of energy derived from fat sources (approximately 47% of energy) under resting conditions. In contrast, the percentage of calories derived from fat during the 5-hour postmeal period decreased from baseline to post-weight loss from 38% +/- 3% to 26% +/- 4% (P < .05) of total calories expended. The reduction in fat oxidation subsequent to a meal may facilitate fat storage, and may be one mechanism by which one regains weight following weight loss.

Aged↗
PubMed1996

Contrasting effects of resistance and aerobic training on body composition and metabolism after diet-induced weight loss.

This study examined whether exercise training facilitates maintenance of body weight at reduced levels following weight loss by attenuating weight loss-induced reductions in resting metabolism and fat oxidation. The effects of 12 weeks (three times per week) of either aerobic or weight training exercise on body weight, body composition, and energy metabolism during rest and following a meal in 18 older (mean +/- SE, 61 +/- 1 years; range, 56 to 70) subjects who had recently lost a mean of 9 +/- 1 kg were studied. During the exercise training period, the aerobic training group (five women, four men) had a significant (P < .05) reduction in body weight (-2.5 +/- 0.6 kg) as compared with the weight training group (five women, four men) (0.4 +/- 0.9 kg). Eight of nine aerobic training subjects lost additional weight, while six of nine weight training subjects gained weight. Neither type of training reversed the depressions in resting metabolism or fat oxidation rates (ie, resting or postprandial) that had occurred as a consequence of the prior weight loss. Thus, alterations in resting metabolism or fat oxidation (resting or postprandial) do not appear to be the mechanism(s) by which exercise training facilitates maintenance of diet-induced weight loss.

Aged↗
PubMed1996

Mixed agonist/antagonist activity of an FK-506-related immunosuppressant: biological and biochemical characterization.

FK-506 blocks T cell activation by preventing lymphokine gene transcription through formation of a complex with FKBP12 that inhibits calcineurin phosphatase activity. Immunosuppressive FK-506 analogs (agonists) have been generated whose potency correlates with calcineurin inhibition. Nonimmunosuppressive antagonist analogs have also been identified, including L-685,818, which binds to FKBP12 but does not inhibit calcineurin. We describe a novel property of FK-506 analog, characterized as a mixed agonist/antagonist immunosuppressive activity. It is displayed by L-688,617, the 32 O-methoxyethoxymethyl derivative of the agonist L-683,590 (C21-ethyl). Although it binds to FKBP12 similarly to L-683,590, L-688,617 incompletely suppressed T cell proliferation induced by optimal activation and enhanced that induced by supraoptimal activation. In the latter situation, L-688,617 suppressed IL-2 production only partially but blocked activation-driven cell death. Moreover, a 1000-fold molar excess of L-688,617 antagonized the immunosuppressive activity of L-683,590. L-688,617 inhibited calcineurin phosphatase activity in cells only partially. The unique agonist/antagonist activity of L-688,617 may therefore reflect its high affinity for FKBP12, combined with a reduced ability of the drug-FKBP12 complex to inhibit calcineurin function. However, in a cell-free system, L-688,617 completely blocked this function when a large excess of FKBP12 over calcineurin was present, suggesting that the intracellular concentration of FKBP12 may be a limiting factor that prevents full agonist activity of L-688,617 in cells.

Animals↗
PubMed1994

Inhibition of calcineurin by a novel FK-506-binding protein.

FK-506, a potent immunosuppressive drug, acts during the commitment phase of T-lymphocyte activation to block a subset of calcium-associated events necessary for transcription of certain early lymphokine genes. The drug binds to an abundant, cytosolic 11.8-kDa protein termed the FK-506-binding protein (FKBP12). The FKBP12.FK-506 complex inhibits calcineurin, a calcium-dependent phosphatase that is a component of the signal transduction pathway leading to early lymphokine gene transcription. FKBP12 is one member of a growing gene family. Prior to this report, all other FKBP family members had been irrelevant to the mechanism of action of FK-506 because no other FKBP.FK-506 complexes were able to bind and inhibit calcineurin. Here, we report the purification and characterization of a novel FK-506-binding protein, FKBP12.6. Having 85% amino acid sequence identity to FKBP12, FKBP12.6 is, among the FKBPs, most closely related to FKBP12. When complexed with FK-506, FKBP12.6 binds to and inhibits calcineurin, making it only the second FKBP discovered thus far to do so. The ability to inhibit calcineurin establishes the potential relevance of FKBP12.6 to the immunosuppressive or toxic side effects of FK-506.

Amino Acid Isomerases↗
PubMed1991

FKBP, the binding protein for the immunosuppressive drug, FK-506, is not an inhibitor of protein kinase C activity.

Recently, the amino acid sequence of a 12 Kd endogenous protein inhibitor of protein kinase C (PKC-I 2) has been shown to be identical to that of the 12 KDa receptor for the immunosuppressive drug, FK-506. In view of this observation we examined the effects of recombinant and native human FKBP on protein kinase C (PKC) activity. FKBP, at molar concentrations up to 1900-fold over that of PKC, failed to inhibit PKC phosphorylation of histone H1 and failed to block the auto-phosphorylation of PKC. Interestingly, FKBP is phosphorylated by PKC in these reactions. The phosphorylation of FKBP by PKC appears to be specific since the catalytic subunit of cAMP-dependent protein kinase fails to phosphorylate the binding protein. Our results fail to support a role for FKBP as an inhibitor of protein kinase C.

Animals↗
PubMed1990

The cytosolic-binding protein for the immunosuppressant FK-506 is both a ubiquitous and highly conserved peptidyl-prolyl cis-trans isomerase.

We have recently isolated an abundant cytosolic protein from human T-cells which specifically binds the immunosuppressive agent, FK-506. The FK-506-binding protein (FKBP) is a member of a novel class of proteins possessing peptidyl-prolyl cis-trans isomerase activity. These proteins are believed to play an important role in accelerating the rate at which proteins fold into their native conformations. In the present study, we demonstrate that FKBP is not a lymphoid-specific protein, but is widely distributed and phylogenically conserved. FKBP, purified from three sources (a human T-lymphocyte cell line JURKAT, bovine calf thymus, and Saccharomyces cerevisiae) exhibit identical molecular weights, immunological cross-reactivities, and a high degree of NH2-terminal amino acid sequence homology. In addition, FKBP from all sources possesses peptidyl-prolyl cis-trans isomerase activity which can be specifically inhibited by FK-506. We conclude that FKBP may serve an important biological function in all eukaryotic cells.

Amino Acid Isomerases↗