Pegtel D Michiel, Ellenbroek Saskia I J, Mertens Alexander E E, van der Kammen Rob A, de Rooij Johan, Collard John G
The Netherlands Cancer Institute, Division of Cell Biology, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.
Curr Biol. 2007 Oct 9;17(19):1623-34. doi: 10.1016/j.cub.2007.08.035. Epub 2007 Sep 6.
The establishment and maintenance of cell polarity is crucial for many biological functions and is regulated by conserved protein complexes. The Par polarity complex consisting of Par3, Par6, and PKCzeta, in conjunction with Tiam1-mediated Rac signaling, controls apical-basal cell polarity in contacting epithelial cells. Here we tested the hypothesis that the Par complex, in conjunction with Tiam1, controls "front-rear" polarity during the persistent migration of freely migrating keratinocytes.
Wild-type (WT) epidermal keratinocytes lacking cell-cell contacts are stably front-rear polarized and migrate persistently. In contrast, Tiam1-deficient (Tiam1 KO) and (si)Par3-depleted keratinocytes are generally unpolarized and migrate randomly because front-rear polarity is short lived. Immunoprecipitation experiments show that in migrating keratinocytes, Tiam1 associates with Par3 and PKCzeta. Moreover, Par3, PKCzeta, and Tiam1 proteins are enriched at the leading edges of polarized keratinocytes. Tiam1 KO keratinocytes are impaired in chemotactic migration toward growth factors, whereaes haptotactic migration is similar to WT. Par3 depletion or the blocking of PKCzeta signaling in WT keratinocytes impairs chemotaxis but has no additional effect on Tiam1 KO cells. The migratory and morphological defects in keratinocytes with impaired Par-Tiam1 function closely resemble cells with pharmacologically destabilized microtubules (MTs). Indeed, MTs in Tiam1 KO keratinocytes and WT cells treated with a PKCzeta inhibitor are unstable, thereby negatively influencing directional but not random migration.
We conclude that the Par-Tiam1 complex stabilizes front-rear polarization of noncontacting migratory cells, thereby stimulating persistent and chemotactic migration, whereas in contacting keratinocytes, the same complex controls the establishment of long-lasting apical-basal polarity. These findings underscore a remarkable flexibility of the Par polarity complex that, depending on the biological context, controls distinct forms of cellular polarity.
细胞极性的建立和维持对许多生物学功能至关重要，且由保守的蛋白质复合物调控。由Par3、Par6和PKCζ组成的Par极性复合物，与Tiam1介导的Rac信号传导一起，控制接触上皮细胞中的顶-基细胞极性。在此，我们检验了这样一个假设，即Par复合物与Tiam1一起，在自由迁移的角质形成细胞持续迁移过程中控制“前-后”极性。
缺乏细胞间接触的野生型（WT）表皮角质形成细胞稳定地呈现前-后极性并持续迁移。相比之下，Tiam1缺陷型（Tiam1 KO）和（si）Par3缺失的角质形成细胞通常无极性且随机迁移，因为前-后极性持续时间较短。免疫沉淀实验表明，在迁移的角质形成细胞中，Tiam1与Par3和PKCζ结合。此外，Par3、PKCζ和Tiam1蛋白在极化角质形成细胞的前缘富集。Tiam1 KO角质形成细胞在向生长因子的趋化迁移中受损，而趋触性迁移与WT相似。WT角质形成细胞中Par3缺失或PKCζ信号传导被阻断会损害趋化性，但对Tiam1 KO细胞没有额外影响。Par-Tiam1功能受损的角质形成细胞中的迁移和形态缺陷与用药物破坏微管（MT）稳定性的细胞非常相似。事实上，用PKCζ抑制剂处理的Tiam1 KO角质形成细胞和WT细胞中的MT不稳定，从而对定向迁移而非随机迁移产生负面影响。
我们得出结论，Par-Tiam1复合物稳定了非接触迁移细胞的前-后极化，从而促进持续和趋化迁移，而在接触的角质形成细胞中，相同的复合物控制持久顶-基极性的建立。这些发现强调了Par极性复合物的显著灵活性，即根据生物学背景控制不同形式的细胞极性。
