Serum factors regulate the expression of the proliferation-related genes α5 integrin and keratin 1, but not keratin 10, in HaCaT keratinocytes

Abstract

In the highly coordinated programme of gene expression during keratinocyte proliferation and differentiation, alpha5 integrin and keratins 1 and 10 (K1/K10) may play important regulatory roles. We were interested in seeing whether, in continuously growing, immortalized HaCaT keratinocytes, similar to normal keratinocytes, the expression of alpha5 integrin and K1/K10 was related to cell proliferation and differentiation. After release from cell quiescence the expression of alpha5 integrin, both at the mRNA and protein levels, was upregulated in the cells. At the same time, K1/K10 mRNA and protein expression decreased dramatically, while the mRNA for D1 cyclin became detectable, and the cells became highly proliferative. These findings indicate that alpha5 integrin and K1/K10 are involved in the regulation of HaCaT proliferation and differentiation, as in normal keratinocytes. However, HaCaT cells are different from normal keratinocytes in their ability to lose K1/K10 expression. There is no evidence that the expression of K1/K10 can be reversed in normal keratinocytes. This ability of dedifferentiation might be a unique feature of HaCaT cells and may be a key component of their immortalized nature. We also found that serum factors regulate mRNA expression of alpha5 integrin and K1, but not of K10, in HaCaT cells. This information could be relevant to the understanding of normal epidermal differentiation.

Wnt/β‐catenin signaling is critical for dedifferentiation of aged epidermal cells in vivo and in vitro

“…Therefore, the data suggested that some of the aged cells in the grafted epidermal sheets had dedifferentiated into stem cell-like cells under the wound microenvironment. This finding is not surprising, because serum factors, which might be similar to those found in the wound microenvironment, can induce the dedifferentiation of HaCaT keratinocytes (Pivarcsi et al, 2001).…”

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Characterization of molecules showing altered expression profile in psoriasis

“…Real-time RT-PCR experiments (n = 3) ( Figure 5A) and Western blot experiments (n = 3) ( Figure 5B) revealed that the NPM mRNA and protein expressions were highest on days 1 and 2 and then gradually declined during the 10-day follow-up. The transcriptional level upregulation of NPM occurred in proliferating cells and, although a slight decline in NPM level was observed, the protein remained at a high level in the less proliferating, more differentiated keratinocytes when the alpha5 integrin was already decreasing [39], suggesting that the NPM protein is relatively stable once expressed in the cells. The fact that the mRNA level decreased rapidly (day 4), while the protein level in the keratinocytes declined in a prolonged, more moderate manner (day 8), indicates that posttranscriptional, translational regulation and posttranslational modifications such as phosphorylation during the maturation and processing of the protein might play important roles in the NPM protein expression in keratinocytes.…”

“…In contrast to that, there was a very lowsometimes undetectable -PRINS expression in the dermis. Taken We have previously demonstrated that the PRINS ncRNA interacts physically with the chaperone molecule nucleophosmin (NPM) 39 . The crucial regulatory roles of NPM in cell proliferation and cellular stress response have already been described 99,100 .…”

“…Szegedi identified nucleophosmin as a putative PRINS-binding protein 39 . NPM is a ubiquitously expressed nuclear phosphoprotein which shuttles continuously between the nucleus and the cytoplasm 86 .…”