Regulator of calcineurin 1 controls growth plasticity of adult pancreas.
OBJECTIVE
Growth of exocrine pancreas is regulated by gastrointestinal hormones, notably cholecystokinin (CCK). CCK-driven pancreatic growth requires calcineurin (CN), which activates Nuclear Factor of Activated T cells (NFATs), but the genetic underpinnings and feedback mechanisms that regulate this response are not known.


METHODS
Pancreatic growth was stimulated by protease inhibitor (PI)-containing chow, which induces secretion of endogenous CCK. Expression profiling of PI stimulation was performed on Affymetrix 430A chips, and CN was inhibited via FK506. Exocrine pancreas-specific overexpression of CN inhibitor Regulator of Calcineurin 1 (Rcan1) was achieved by breeding elastase-Cre(estrogen receptor [ER]) transgenics with "flox-on" Rcan1 mice.


RESULTS
CN inhibitor FK506 blocked expression of 38 genes, as confirmed by quantitative polymerase chain reaction. The CN-dependent genes were linked to growth-related processes, whereas their promoters were enriched in NFAT and NFAT/AP1 sites. Multiple NFAT targets, including Rcan1, Rgs2, HB-EGF, Lif, and Gem, were validated by chromatin immunoprecipitation. One of these, a CN feedback inhibitor Rcan1, was induced >50 fold during 1-8 hours course of pancreatic growth and strongly inhibited (>99%) by FK506. To examine its role in pancreatic growth, we overexpressed Rcan1 in an inducible, acinar-specific fashion. Rcan1 overexpression inhibited CN-NFAT signaling, as shown using an NFAT-luciferase reporter and quantitative polymerase chain reaction. Most importantly, the increase in exocrine pancreas size, protein/DNA content, and acinar proliferation were all blocked in Rcan1 overexpressing mice.


CONCLUSIONS
We profile adaptive pancreatic growth, identify Rcan1 as an important new feedback regulator, and firmly establish that CN-NFAT signaling is required for this response.
Gurda
Grzegorz T
GT
Department of Molecular and Integrative Physiology, The University of Michigan Medical School, Ann Arbor, Michigan, USA. ggurda1@jhmi.edu
Crozier
Stephen J
SJ
Ji
Baoan
B
Ernst
Stephen A
SA
Logsdon
Craig D
CD
Rothermel
Beverly A
BA
Williams
John A
JA
D000818:Animals; D019703:Calcineurin / Q000378:metabolism; D065095:Calcineurin Inhibitors; D002135:Calcium-Binding Proteins; D049109:Cell Proliferation; D002766:Cholecystokinin / Q000378:metabolism*; D004032:Diet; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004952:Esters; D025461:Feedback, Physiological; D016670:Gabexate / Q000008:administration & dosage / Q000031:analogs & derivatives; D020869:Gene Expression Profiling / Q000379:methods; D005786:Gene Expression Regulation; D006146:Guanidines; D019426:Integrases / Q000235:genetics; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D008822:Mice, Transgenic; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D050778:NFATC Transcription Factors / Q000378:metabolism; D041681:NIH 3T3 Cells; D020411:Oligonucleotide Array Sequence Analysis; D009929:Organ Size; D010179:Pancreas / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D010196:Pancreatic Elastase / Q000235:genetics; D011480:Protease Inhibitors / Q000008:administration & dosage; D043886:Receptor, Cholecystokinin A / Q000235:genetics / Q000378:metabolism; D011960:Receptors, Estrogen / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D016559:Tacrolimus / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection
D065095:Calcineurin Inhibitors; D002135:Calcium-Binding Proteins; C511512:DSCR1 protein, mouse; D004791:Enzyme Inhibitors; D004952:Esters; D006146:Guanidines; D047908:Intracellular Signaling Peptides and Proteins; D009124:Muscle Proteins; D050778:NFATC Transcription Factors; D011480:Protease Inhibitors; D043886:Receptor, Cholecystokinin A; D011960:Receptors, Estrogen; C034532:camostat; D016670:Gabexate; D002766:Cholecystokinin; C045073:Cre recombinase; D019426:Integrases; D019703:Calcineurin; D010196:Pancreatic Elastase; D016559:Tacrolimus