Cytokines activate genes of the endocytotic pathway in insulin-producing RINm5F cells.
OBJECTIVE
Cytokines are important humoral mediators of beta cell destruction in autoimmune diabetes. The aim of this study was to identify novel cytokine-induced genes in insulin-producing RINm5F cells, which may contribute to beta cell death or survival.


METHODS
A global gene expression profile in cytokine-exposed insulin-producing RINm5F cells was achieved by automated restriction fragment differential display PCR. The expression of selected candidate genes was confirmed by real-time RT-PCR analysis.


RESULTS
Exposure of RINm5F cells to IL-1beta or to a cytokine mixture (IL-1beta, TNF-alpha, IFN-gamma) for 6 h resulted in the differential expression of a functional gene cluster. Apart from the well-known up-regulation of the cytokine-responsive genes iNOS, NF-kappaB, MnSOD and Hsp70, several genes that belong to the functional cluster of the endocytotic pathway were identified. These endocytotic genes comprised: clathrin, megalin, synaptotagmin and calcineurin, which were up-regulated by IL-1beta or the cytokine mixture. In contrast, the expression of the calcineurin inhibitor CAIN and of the GDP/GTP exchange protein Rab3 was down-regulated by cytokines. Other up-regulated cytokine-responsive genes were: agrin, murine adherent macrophage protein mRNA ( MAMA) and transport-associated protein ( TAP1/MTP), whereas the plasma membrane calcium ATPase ( PMCA) 2 and PMCA 3 genes were down-regulated by cytokines.


CONCLUSIONS
Our results indicate that genes of the endocytotic pathway are regulated by pro-inflammatory cytokines. This might affect the density of cytokine receptors at the beta cell surface and concomitantly the sensitivity of the cells to cytokine toxicity. A better understanding of the functional cross-talk between endocytotic and cytokine signalling pathways could further the development of novel strategies to protect pancreatic beta cells against toxic effects of pro-inflammatory cytokines.
Souza
K L A
KLA
Institute of Clinical Biochemistry, Hanover Medical School, 30623, Hanover, Germany.|Department of Cell Biology and Genetics, University of Maringá, Maringá, Brazil.
Elsner
M
M
Institute of Clinical Biochemistry, Hanover Medical School, 30623, Hanover, Germany.
Mathias
P C F
PCF
Department of Cell Biology and Genetics, University of Maringá, Maringá, Brazil.
Lenzen
S
S
Institute of Clinical Biochemistry, Hanover Medical School, 30623, Hanover, Germany.
Tiedge
M
M
Institute of Clinical Biochemistry, Hanover Medical School, 30623, Hanover, Germany. tiedge.markus@mh-hannover.de.
D018171:Agrin / Q000235:genetics; D000818:Animals; D001483:Base Sequence; D045744:Cell Line, Tumor; D016207:Cytokines / Q000276:immunology*; D017931:DNA Primers; D015972:Gene Expression Regulation, Neoplastic / Q000276:immunology*; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007340:Insulinoma; D009363:Neoplasm Proteins / Q000235:genetics; D010190:Pancreatic Neoplasms; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats
D018171:Agrin; D016207:Cytokines; D017931:DNA Primers; D007328:Insulin; D009363:Neoplasm Proteins; D012333:RNA, Messenger