Processing of SCF isoform 1

SCF exists as two alternatively spliced variants, a soluble form and a membrane-bound form differing in one exon (exon 6). Both isoforms are initially membrane bound with an extracellular domain, a transmembrane segment and an intracellular region. The longer isoform is rapidly cleaved to generate a 165 aa soluble protein knows as sSCF. The SCF transcript that lacks exon 6 encodes a glycoprotein that remains membrane-bound (mSCF). Both mSCF and sSCF are bioactive but different in their efficacy in c-kit activation.<br>Proteases including matrix metalloprotease-9 (Heissig et al., 2002), Chymase-1 (Longley et al., 1997) and several members of the ADAMs family (Kawaguchi et al, 2007; Amour et al, 2002; Chesneau et al, 2003; Mohan et al, 2002; Roghani et al, 1999; Zou et al, 2004) have been suggested to have a role in the processing of sSCF.

SCF 存在两种可选择性剪接的变体，一种为可溶性形式，另一种为膜结合形式，两者在第六外显子（exon 6）上存在差异。两种异构体最初均为膜结合状态，具有细胞外结构域、跨膜段和细胞内区域。较长的异构体迅速被切割，生成一种由165个氨基酸组成的可溶性蛋白质，称为sSCF。缺乏第六外显子的SCF转录本编码的糖蛋白保持膜结合状态（mSCF）。mSCF和sSCF均具有生物活性，但在c-kit激活的效力上存在差异。<br>包括基质金属蛋白酶-9（Heissig等，2002年）、Chymase-1（Longley等，1997年）以及ADAMs家族的多个成员（Kawaguchi等，2007年；Amour等，2002年；Chesneau等，2003年；Mohan等，2002年；Roghi等，1999年；Zou等，2004年）在内的蛋白酶被认为在sSCF的加工过程中发挥重要作用。