Mouse macrophages show different requirements for phosphatidylserine receptor Tim4 in efferocytosis
Mouse macrophages show different requirements for phosphatidylserine receptor Tim4 in efferocytosis
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DOI：
10.1073/pnas.1705365114
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发表时间：
2017-08
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影响因子：
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通讯作者：
Yuichi Yanagihashi;Katsumori Segawa;R. Maeda;Y. Nabeshima;S. Nagata
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作者：
Yuichi Yanagihashi;Katsumori Segawa;R. Maeda;Y. Nabeshima;S. Nagata
每天有数十亿细胞发生凋亡，暴露出磷脂酰丝氨酸（PtdSer），并以PtdSer依赖性方式被巨噬细胞吞噬。在这里，我们提出Tim 4（一种PtdSer受体）强烈增强了表达TAM受体的吞噬细胞诱导的蛋白S或生长停滞特异性6诱导的胞吐作用。居民的腹腔巨噬细胞，枯否细胞，和CD 169+皮肤巨噬细胞需要Tim 4的有效的巨噬细胞，而巯基乙酸引起的腹腔巨噬细胞和培养的小胶质细胞没有。这些结果表明，不同的巨噬细胞的吞噬作用可能有不同的生理结果，因此，将有助于理解巨噬细胞的异质性。蛋白S（ProS）和生长停滞特异性6（Gas 6）与磷脂酰丝氨酸（PtdSer）结合，并在结合TAM家族受体（Tyro 3、Axl和Mer）后诱导胞浆细胞增多。在此，我们在HEK 293 T细胞中产生了与IgG片段可结晶区融合的小鼠ProS、Gas 6和TAM受体胞外区。ProS和Gas 6依赖于PtdSer（Kd 20-40 nM）、Mer和Tyro 3（Kd 15-50 nM）结合Ca 2+。Gas 6强烈结合Axl（Kd < 1.0 nM），但ProS不结合Axl。使用NIH 3 T3为基础的细胞系表达一个单一的TAM受体，我们表明，TAM介导的红细胞增多症是由受体结合能力的ProS和Gas 6。Tim 4是一种与PtdSer强烈结合的膜蛋白。单独的Tim 4不支持巨噬细胞增多，但增强TAM依赖性巨噬细胞增多。居民的腹腔巨噬细胞，枯否细胞，和CD 169+皮肤巨噬细胞需要TIM 4 TAM刺激的巨噬细胞，而巯基乙酸酯引起的巨噬细胞或原代培养的小胶质细胞的巨噬细胞是TAM依赖性，但不是Tim 4依赖性。这些结果表明，TAM和Tim 4在某些巨噬细胞群体中协同有效的巨噬细胞作用。
Significance Every day, billons of cells undergo apoptosis, expose phosphatidylserine (PtdSer), and are engulfed by macrophages in a PtdSer-dependent manner. Here, we present that Tim4, a PtdSer receptor, strongly enhances Protein S- or growth arrest-specific 6-induced efferocytosis by TAM receptor-expressing phagocytes. Resident peritoneal macrophages, Kupffer cells, and CD169+ skin macrophages required Tim4 for the efficient efferocytosis, whereas thioglycollate-elicited peritoneal macrophages and cultured microglia did not. These results indicate that the efferocytosis by different macrophages may have different physiological outcomes and, therefore, would contribute to the understanding of macrophage heterogeneity. Protein S (ProS) and growth arrest-specific 6 (Gas6) bind to phosphatidylserine (PtdSer) and induce efferocytosis upon binding TAM-family receptors (Tyro3, Axl, and Mer). Here, we produced mouse ProS, Gas6, and TAM-receptor extracellular region fused to IgG fragment crystallizable region in HEK293T cells. ProS and Gas6 bound Ca2+ dependently to PtdSer (Kd 20–40 nM), Mer, and Tyro3 (Kd 15–50 nM). Gas6 bound Axl strongly (Kd < 1.0 nM), but ProS did not bind Axl. Using NIH 3T3-based cell lines expressing a single TAM receptor, we showed that TAM-mediated efferocytosis was determined by the receptor-binding ability of ProS and Gas6. Tim4 is a membrane protein that strongly binds PtdSer. Tim4 alone did not support efferocytosis, but enhanced TAM-dependent efferocytosis. Resident peritoneal macrophages, Kupffer cells, and CD169+ skin macrophages required Tim4 for TAM-stimulated efferocytosis, whereas efferocytosis by thioglycollate-elicited peritoneal macrophages or primary cultured microglia was TAM dependent, but not Tim4 dependent. These results indicate that TAM and Tim4 collaborate for efficient efferocytosis in certain macrophage populations.