Distinct Regulatory Functions of Calpain 1 and 2 during Neural Stem Cell Self-Renewal and Differentiation

Abstract

Calpains are calcium regulated cysteine proteases that have been described in a wide range of cellular processes, including apoptosis, migration and cell cycle regulation. In addition, calpains have been implicated in differentiation, but their impact on neural differentiation requires further investigation. Here, we addressed the role of calpain 1 and calpain 2 in neural stem cell (NSC) self-renewal and differentiation. We found that calpain inhibition using either the chemical inhibitor calpeptin or the endogenous calpain inhibitor calpastatin favored differentiation of NSCs. This effect was associated with significant changes in cell cycle-related proteins and may be regulated by calcium. Interestingly, calpain 1 and calpain 2 were found to play distinct roles in NSC fate decision. Calpain 1 expression levels were higher in self-renewing NSC and decreased with differentiation, while calpain 2 increased throughout differentiation. In addition, calpain 1 silencing resulted in increased levels of both neuronal and glial markers, β-III Tubulin and glial fibrillary acidic protein (GFAP). Calpain 2 silencing elicited decreased levels of GFAP. These results support a role for calpain 1 in repressing differentiation, thus maintaining a proliferative NSC pool, and suggest that calpain 2 is involved in glial differentiation.

Thromboxane Governs the Differentiation of Adipose-Derived Stromal Cells Toward Endothelial Cells In Vitro and In Vivo

“…Inhibition of calpain protease in ASCs re-expressing TP suppressed β-catenin degradation and enhanced β-catenin/T-cell factor transcriptional activity and angiogenic potential in ASCs, indicating that the reduction in calpain-mediated β-catenin degradation contributed to the elevated endothelial differentiation of TP-KO ASCs. Moreover, calpain is involved in the suppression of Wnt/β-catenin signaling, 36,37 which is in agreement with our observations and calpain suppressed the differentiation of stem cells toward neurons 71 and skeletal muscle cells. 72,73 However, calpain-mediated N-terminal truncation of β-catenin may enhance T-cell factor-dependent transcription by increasing accumulation of active 75-kDa β-catenin protein in some tissues or cancers.…”

Expression of nestin-associated genes in the inner ear of newborn rats following injury and hypoxia

“…Coexpression changes between Nes and Casp3 transcripts were reported previously in traumatic brain injury [54] . Calpain 1 and calpain 2 were found to have distinct roles to play in neural stem cell self-renewal and differentiation [55] . The down-regulation of the calpain subunits may contribute to preserving or repairing the cytoskeleton [56] .…”

Tauroursodeoxycholic acid increases neural stem cell pool and neuronal conversion by regulating mitochondria-cell cycle retrograde signaling

“…[62][63][64] NSCs were grown in monolayer and routinely maintained, as previously described. 15,65 Neural differentiation was performed by first platting NSCs in undifferentiation medium onto uncoated tissue culture plastic dishes at 6.5 £ 10 5 cells/mL for 24 h, and changing the culture medium to an optimized neuronal differentiation-inducing medium, comprising Euromed-N medium supplemented with 10 ng/mL bFGF, 0.5% N-2 supplement, 1% B27 supplement (17504-044; Invitrogen …”