Role of Tropomodulin鈥檚 Leucine Rich Repeat Domain in the Formation of Neurite-like Processes

详细信息    查看全文

• 作者：Laurent Guillaud ; Kevin T. Gray ; Natalia Moroz ; Caroline Pantazis ; Edward Pate ; Alla S. Kostyukova
• 刊名：Biochemistry
• 出版年：2014
• 出版时间：April 29, 2014
• 年：2014
• 卷：53
• 期：16
• 页码：2689-2700
• 全文大小：529K
• 年卷期：v.53,no.16(April 29, 2014)
• ISSN：1520-4995

文摘

Actin dynamics is fundamental for neurite development; monomer depolymerization from pointed ends is rate-limiting in actin treadmilling. Tropomodulins (Tmod) make up a family of actin pointed end-capping proteins. Of the four known isoforms, Tmod1鈥揟mod3 are expressed in brain cells. We investigated the role of Tmod鈥檚 C-terminal (LRR) domain in the formation of neurite-like processes by overexpressing Tmod1 and Tmod2 with deleted or mutated LRR domains in PC12 cells, a model system used to study neuritogenesis. Tmod1 overexpression results in a normal quantity and a normal length of processes, while Tmod2 overexpression reduces both measures. The Tmod2 overexpression phenotype is mimicked by overexpression of Tmod1 with the LRR domain removed or with three point mutations in the LRR domain that disrupt exposed clusters of conserved residues. Removal of Tmod2鈥檚 LRR domain does not significantly alter the outgrowth of neurite-like processes compared to that of Tmod2. Overexpression of chimeras with the N-terminal and C-terminal domains switched between Tmod1 and Tmod2 reinforces the idea that Tmod1鈥檚 LRR domain counteracts the reductive effect of the Tmod N-terminal domain upon formation of processes while Tmod2鈥檚 LRR domain does not. We suggest that the TM-dependent actin capping ability of both Tmods inhibits the formation of processes, but in Tmod1, this inhibition can be controlled via its LRR domain. Circular dichroism, limited proteolysis, and molecular dynamics demonstrate structural differences in the C-terminal region of the LRR domains of Tmod1, Tmod2, and the Tmod1 mutant.