Cell coupling regulates Ins1, Pdx-1 and MafA to promote insulin secretion in mouse pancreatic beta cells

The intracellular contact between pancreatic β-cells plays an important role in functional insulin secretion. We propose cell coupling may regulate glucose-stimulated insulin gene expression. MIN-6, a murine β-cell line, was cultured on the Lipidure-coat dish for cell clusters formation. The responses to glucose-stimulation between monolayers and clusters were compared. The coupling of β-cells was evaluated by immunohistochemical (IHC) staining. After the establishment of cell coupling was confirmed, the transcription factors of insulin gene expression were assessed by RT-PCR. Results showed that in addition to secrete insulin in a glucose-regulated manner, MIN-6 clusters had biphasic insulin secretion. Relative to monolayer, clusters have higher stimulation-index and lower constitutive insulin release. IHC staining showed the connexin 36 highly expressed in clusters. Compared with monolayers, the mRNA expression of insulin 1 (Ins1) and homeodomain transcription factor pancreatic/duodenal homebox-1 (Pdx-1) of clusters were downregulated in low glucose level. On the contrary, these gene expressions were upregulated when clusters cultured in high glucose environment. The V-maf musculoaponeurotic fibrosarcoma oncogene homologue A (MafA) was relative highly expressed in clusters under high glucose condition. This study reveals that cell coupling regulates glucose-stimulated insulin gene expression to promote insulin secretion in mouse β-cells.