2013年7月8日，清華大學(xué)生命科學(xué)學(xué)院潘俊敏教授研究組在《美國科學(xué)院院刊》（PNAS）上在線發(fā)表了題為“Activation loop phosphorylation of a protein kinase is a molecular marker of organelle size that dynamically reports flagellar length”的研究論文,，報(bào)道了蛋白激酶CALK在纖毛長度調(diào)控體系中的作用,，該工作證實(shí)細(xì)胞存在纖毛長度感知系統(tǒng)，實(shí)現(xiàn)自身纖毛長度的主動(dòng)調(diào)控,。
纖毛是真核生物一種保守的細(xì)胞器官,，纖毛的缺陷會(huì)造成眾多的人類疾病和發(fā)育異常,。因此研究纖毛長度調(diào)控不僅可以解答細(xì)胞器大小調(diào)控這一基本的生物學(xué)問題，還可以為纖毛相關(guān)疾病的研究提供新的線索,。纖毛長度調(diào)控理論目前還存在很大的爭論,，主要爭議點(diǎn)為纖毛長度調(diào)控是細(xì)胞的主動(dòng)行為還是被動(dòng)行為。
該工作發(fā)現(xiàn)CALK激酶活性調(diào)控關(guān)鍵位點(diǎn)T193磷酸化和纖毛長度之間有密切關(guān)系,，在纖毛組裝和解聚兩個(gè)過程中,，T193位點(diǎn)磷酸化修飾比例都隨著纖毛長度發(fā)生線性變化。進(jìn)一步的研究發(fā)現(xiàn)纖毛長度突變體和環(huán)境誘導(dǎo)的纖毛長度異常的野生型細(xì)胞也有類似現(xiàn)象,。該研究證實(shí)細(xì)胞存在纖毛長度感知體系實(shí)時(shí)感受纖毛長度,，并可以將纖毛長度信號(hào)轉(zhuǎn)化為蛋白質(zhì)磷酸化修飾信號(hào)，反饋調(diào)控纖毛長度,。該工作對(duì)于細(xì)胞器大小調(diào)控具有普遍意義，說明細(xì)胞很可能廣泛的存在細(xì)胞器主動(dòng)感知系統(tǒng),，并主動(dòng)調(diào)控其自身細(xì)胞器體積來適應(yīng)細(xì)胞要求,。
這是潘俊敏教授研究組繼2011年在《Current Biology》上發(fā)表纖毛長度調(diào)控研究后的又一重大發(fā)現(xiàn)，為細(xì)胞器大小調(diào)控理論提供了新的理論,。該工作是由博士生曹木青同學(xué)為主,，并與美國西南醫(yī)學(xué)中心共同合作完成。（生物谷Bioon.com）
doi:10.1073/pnas.1302364110
PMC:
PMID:
Activation loop phosphorylation of a protein kinase is a molecular marker of organelle size that dynamically reports flagellar length
Muqing Caoa, Dan Menga, Liang Wanga, Shuqing Beib, William J. Snellc,1, and Junmin Pana,1
Specification of organelle size is crucial for cell function, yet we know little about the molecular mechanisms that report and regulate organelle growth and steady-state dimensions. The biflagellated green alga Chlamydomonas requires continuous-length feedback to integrate the multiple events that support flagellar assembly and disassembly and at the same time maintain the sensory and motility functions of the organelle. Although several length mutants have been characterized, the requisite molecular reporter of length has not been identified. Previously, we showed that depletion of Chlamydomonas aurora-like protein kinase CALK inhibited flagellar disassembly and that a gel-shift–associated phosphorylation of CALK marked half-length flagella during flagellar assembly. Here, we show that phosphorylation of CALK on T193, a consensus phosphorylation site on the activation loop required for kinase activity, is distinct from the gel-shift–associated phosphorylation and is triggered when flagellar shortening is induced, thereby implicating CALK protein kinase activity in the shortening arm of length control. Moreover, CALK phosphorylation on T193 is dynamically related to flagellar length. It is reduced in cells with short flagella, elevated in the long flagella mutant, lf4, and dynamically tracks length during both flagellar assembly and flagellar disassembly in WT, but not in lf4. Thus, phosphorylation of CALK in its activation loop is implicated in the disassembly arm of a length feedback mechanism and is a continuous and dynamic molecular marker of flagellar length during both assembly and disassembly.
