Cabezas Alicia, Pattni Krupa, Stenmark Harald
Department of Biochemistry, The Norwegian Radium Hospital, Montebello, N-0310 Oslo, Norway.
Gene. 2006 Apr 12;371(1):34-41. doi: 10.1016/j.gene.2005.11.009. Epub 2006 Jan 31.
Yeast Fab1 is a phosphatidylinositol 3-phosphate 5-kinase involved in endocytic membrane traffic and vacuole homeostasis. Here we have cloned and sequenced the cDNA for the human homologue of Fab1, PIKfyve. The cDNA has an open reading frame of 6294 bp and encodes a 2098-amino acid protein with a calculated molecular mass of 237 kDa, containing a phosphatidylinositol 3-phosphate-binding FYVE domain, a DEP domain, a chaperonin-like domain, and a phosphoinositide kinase domain. The human genome contains a single PIKfyve gene, which comprises 38 exons on chromosomal locus 2q34. PIKfyve is expressed as a single molecular species in a number of human cell lines derived from different tissues. The exogenously expressed protein was found to localize mainly to early endosomes containing two other FYVE domain proteins, EEA1 and Hrs. The endosomal membrane localization of PIKfyve was studied in more detail by examining cells transfected with a constitutively active mutant of the small GTPase Rab5, whose expression results in the enlargement of early endosomes. We show that PIKfyve is distributed in microdomains that are distinct from those occupied by EEA1 and Hrs.
酵母Fab1是一种参与内吞膜运输和液泡稳态的磷脂酰肌醇3-磷酸5-激酶。在此，我们克隆并测序了Fab1的人类同源物PIKfyve的cDNA。该cDNA具有6294 bp的开放阅读框，编码一个2098个氨基酸的蛋白质，计算分子量为237 kDa，包含一个磷脂酰肌醇3-磷酸结合FYVE结构域、一个DEP结构域、一个伴侣蛋白样结构域和一个磷酸肌醇激酶结构域。人类基因组包含一个单一的PIKfyve基因，其在染色体位点2q34上由38个外显子组成。PIKfyve在源自不同组织的多种人类细胞系中以单一分子形式表达。发现外源表达的蛋白主要定位于含有另外两种FYVE结构域蛋白EEA1和Hrs的早期内体。通过检测用小GTP酶Rab5的组成型活性突变体转染的细胞，更详细地研究了PIKfyve在内体膜上的定位，Rab5的表达导致早期内体增大。我们表明，PIKfyve分布在与EEA1和Hrs所占据的微结构域不同的微结构域中。
