Schrader M, Krieglstein K, Fahimi H D
Division of Medical Cell Biology, Institute for Anatomy and Cell Biology, University of Heidelberg, Germany.
Eur J Cell Biol. 1998 Feb;75(2):87-96. doi: 10.1016/s0171-9335(98)80051-4.
We showed recently the plasticity of the peroxisomal compartment in the human hepatoblastoma cell line HepG2 as evidenced by the presence of elongated tubular peroxisomes measuring up to 5 microm next to much smaller spherical or rod-shaped ones (0.1-0.3 microm). Since the occurrence of tubular peroxisomes in a given cell in culture is synchronized, with neighboring cells containing either small spherical or elongated tubular peroxisomes, cell counting of immunofluorescence preparations stained for catalase was used for the quantitative assessment of the dynamics of the peroxisomal compartment and the factors regulating this process. Initial studies revealed that the formation of tubular peroxisomes is primarily influenced by the cell density as well as by lipid- and protein-factors in fetal calf serum, being independent of an intact microtubular network. Biochemical studies showed that the occurrence of tubular peroxisomes correlated with the expression of the mRNA for 70 kDa peroxisomal membrane protein (PMP70), but not with that of matrix proteins. By cultivation of cells in serum- and protein-free media specific factors were identified which influenced the formation of tubular peroxisomes. Among several growth factors tested, nerve growth factor (NGF) was the most potent one inducing tubular peroxisomes and its effect was blocked by K252b, a specific inhibitor of neurotrophin receptor pathway, suggesting the involvement of signal transduction in this process. Furthermore, from several polyunsaturated fatty acids (PUFA) which all induced tubular peroxisomes, the arachidonic acid (AA) was the most potent one. Our observations suggest that tubular peroxisomes are transient structures in the process of rapid expansion of the peroxisomal compartment which are induced either by specific growth factors or by polyunsaturated fatty acids both of which are involved in intracellular signaling.
我们最近发现，人肝癌细胞系HepG2中过氧化物酶体区室具有可塑性，证据是存在长达5微米的细长管状过氧化物酶体，旁边还有小得多的球形或杆状过氧化物酶体（0.1 - 0.3微米）。由于培养中给定细胞内管状过氧化物酶体的出现是同步的，相邻细胞要么含有小球形过氧化物酶体，要么含有细长管状过氧化物酶体，因此对过氧化氢酶染色的免疫荧光制剂进行细胞计数，用于定量评估过氧化物酶体区室的动态变化以及调节这一过程的因素。初步研究表明，管状过氧化物酶体的形成主要受细胞密度以及胎牛血清中的脂质和蛋白质因子影响，与完整的微管网络无关。生化研究表明，管状过氧化物酶体的出现与70 kDa过氧化物酶体膜蛋白（PMP7）的mRNA表达相关，但与基质蛋白的表达无关。通过在无血清和无蛋白培养基中培养细胞，确定了影响管状过氧化物酶体形成的特定因子。在测试的几种生长因子中，神经生长因子（NGF）是诱导管状过氧化物酶体最有效的因子，其作用被神经营养素受体途径的特异性抑制剂K252b阻断，表明信号转导参与了这一过程。此外，在所有能诱导管状过氧化物酶体的多不饱和脂肪酸（PUFA）中，花生四烯酸（AA）是最有效的。我们的观察结果表明，管状过氧化物酶体是过氧化物酶体区室快速扩张过程中的瞬时结构，由特定生长因子或多不饱和脂肪酸诱导，这两者都参与细胞内信号传导。
