Fenech Emma J, Kupervaser Meital, Boshnakovska Angela, Ravid Shani, Castro Inês Gomes, Asraf Yeynit, Callegari Sylvie, Lenz Christof, Urlaub Henning, Rehling Peter, Schuldiner Maya
Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.
The de Botton Institute for Protein Profiling, G-INCPM, Weizmann Institute of Science, Rehovot, Israel.
Contact (Thousand Oaks). 2025 Apr 17;8:25152564251321770. doi: 10.1177/25152564251321770. eCollection 2025 Jan-Dec.
Membrane contact sites are molecular bridges between organelles that are sustained by tethering proteins and enable organelle communication. The endoplasmic reticulum (ER) membrane harbors many distinct families of tether proteins that enable the formation of contacts with all other organelles. One such example is the LAM (Lipid transfer protein Anchored at Membrane contact sites) family in yeast, which is composed of six members, each containing a putative lipid binding and transfer domain and an ER-embedded transmembrane segment. The family is divided into three homologous pairs each unique in their molecular architecture and localization to different ER subdomains. However, what determines the distinct localization of the different LAMs and which specific roles they carry out in each contact are still open questions. To address these, we utilized a labeling approach to profile the proximal protein landscape of the entire family. Focusing on unique, candidate interactors we could support that Lam5 resides at the ER-mitochondria contact site and demonstrate a role for it in sustaining mitochondrial activity. Capturing shared, putative interactors of multiple LAMs, we show how the Lam1/3 and Lam2/4 paralogous pairs could be associated specifically with the plasma membrane. Overall, our work provides new insights into the regulation and function of the LAM family members. More globally it demonstrates how proximity labeling can help identify the shared or unique functions of paralogous proteins.
膜接触位点是由拴系蛋白维持的细胞器之间的分子桥梁，能够实现细胞器间的通讯。内质网（ER）膜含有许多不同的拴系蛋白家族，这些蛋白能与所有其他细胞器形成接触。酵母中的LAM（锚定在膜接触位点的脂质转移蛋白）家族就是这样一个例子，它由六个成员组成，每个成员都包含一个假定的脂质结合和转移结构域以及一个嵌入内质网的跨膜片段。该家族分为三个同源对，每一对在分子结构和定位于不同内质网亚结构域方面都独具特色。然而，是什么决定了不同LAM的独特定位，以及它们在每个接触位点发挥哪些具体作用，仍是悬而未决的问题。为了解决这些问题，我们采用了一种标记方法来描绘整个家族的近端蛋白质图谱。聚焦于独特的候选相互作用蛋白，我们证实Lam5定位于内质网-线粒体接触位点，并证明其在维持线粒体活性方面的作用。通过捕获多个LAM的共同假定相互作用蛋白，我们展示了Lam1/3和Lam2/4同源对如何能够特异性地与质膜相关联。总体而言，我们的工作为LAM家族成员的调控和功能提供了新的见解。更广泛地说，它展示了邻近标记如何有助于识别同源蛋白的共同或独特功能。
