Early and Late G1/S Cyclins and Cdks Act Complementarily to Enhance Authentic Human β-Cell Proliferation and Expansion

Abstract

β-Cell regeneration is a key goal of diabetes research. Progression through the cell cycle is associated with retinoblastoma protein (pRb) inactivation via sequential phosphorylation by the “early” cyclins and cyclin-dependent kinases (cdks) (d-cyclins cdk4/6) and the “late” cyclins and cdks (cyclin A/E and cdk1/2). In β-cells, activation of either early or late G1/S cyclins and/or cdks is an efficient approach to induce cycle entry, but it is unknown whether the combined expression of early and late cyclins and cdks might have synergistic or additive effects. Thus, we explored whether a combination of both early and late cyclins and cdks might more effectively drive human β-cell cell cycle entry than either group alone. We also sought to determine whether authentic replication with the expansion of adult human β-cells could be demonstrated. Late cyclins and cdks do not traffic in response to the induction of replication by early cyclins and cdks in human β-cells but are capable of nuclear translocation when overexpressed. Early plus late cyclins and cdks, acting via pRb phosphorylation on distinct residues, complementarily induce greater proliferation in human β-cells than either group alone. Importantly, the combination of early and late cyclins and cdks clearly increased human β-cell numbers in vitro. These findings provide additional insight into human β-cell expansion. They also provide a novel tool for assessing β-cell expansion in vitro.

Molecular diversity of phenothiazines: design and synthesis of phenothiazine–dithiocarbamate hybrids as potential cell cycle blockers

“…As shown in Fig. 5c, our results verified that cyclin D-CDK4 complex accumulation promotes G1–S transition in cell cycle [27]. Compound 8a downregulated cyclin D1 and CDK4 concentration dependently (Fig.…”

Age-dependent human β cell proliferation induced by glucagon-like peptide 1 and calcineurin signaling

“…Juvenile islets were isolated at the Institute of Cellular Therapeutics of the Allegheny Health Network (Pittsburgh, Pennsylvania, USA) as previously described (3,4,26). Islets from 12 adult donors (ages 20,21,29,30,40,43,43,48,49,53,60, and 60 years, BMI ranges 24.1-29.6) were obtained from the Integrated Islet Distribution Program (http://iidp.coh.org). Islet function (i.e., glucose-induced insulin secretion) was assessed by islet perifusion assay on the day of arrival, as previously described (57,58).…”

Replicative capacity of β-cells and type 1 diabetes

“…In human β-cells the majority of cyclins and cdks are sequestered in the cytoplasm rather than the nucleus, which may contribute to the reluctance of human β-cells to proliferate basally [22,24]. Indeed, there is evidence that cytoplasmic and nuclear trafficking play a regulatory role in human β-cell proliferation [27]. Once in the nucleus, cell cycle molecules can be influenced by additional proteins like menin, which further controls β-cell transcription and replication by modulating methylation activity [28].…”