Role of Dimerization of the Membrane-associated Growth Factor Kit Ligand in Juxtacrine Signaling: The Sl17H Mutation Affects Dimerization and Stability—Phenotypes in Hematopoiesis

Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
Journal of Experimental Medicine (Impact Factor: 12.52). 06/1998; 187(9):1451-61. DOI: 10.1084/jem.187.9.1451
Source: PubMed


The Kit ligand (KL)/Kit receptor pair functions in hematopoiesis, gametogenesis, and melanogenesis. KL is encoded at the murine steel (Sl) locus and encodes a membrane growth factor which may be proteolytically processed to produce soluble KL. The membrane-associated form of KL is critical in mediating Kit function in vivo. Evidence for a role of cytoplasmic domain sequences of KL comes from the Sl17H mutation, a splice site mutation that replaces the cytoplasmic domain with extraneous amino acids. Using deletion mutants and the Sl17H allele, we have investigated the role of the cytoplasmic domain sequences of KL in biosynthetic processing and cell surface presentation. The normal KL protein products are processed for cell surface expression, where they form dimers. Both Sl17H and the cytoplasmic deletion mutants of KL were processed to the cell surface; however, the rate of transport and protein stability were affected by the mutations. Deletion of cytoplasmic domain sequences of KL did not affect dimerization of KL. In contrast, dimerization of the Sl17H protein was reduced substantially. In addition, we have characterized the hematopoietic cell compartment in Sl17H mutant mice. The Sl17H mutation has only minor effects on hematopoiesis. Tissue and peritoneal mast cell numbers were reduced in mutant mice as well as in myeloid progenitors. Interestingly, long-term bone marrow cultures from Sl17H mice did not sustain the long-term production of hematopoietic cells. In addition, homing of normal hematopoietic progenitors to the spleen of irradiated Sl17H/Sl17H recipient mice was diminished in transplantation experiments, providing evidence for a role of Kit in homing or lodging. These results demonstrate that the membrane forms of KL exist as homodimers on the cell surface and that dimerization may play an important role in KL/Kit-mediated juxtacrine signaling.

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Available from: Youichi Tajima
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    • "In contrast to other hematopoietic cell progeny they express Kit and they depend on KitL for their survival, growth and function (Oliveira and Lukacs, 2003). A mast cell deficit is a common feature of mice with Kit and KitL loss of function mutations including KitL Sl17H/Sl17H mice (Tajima et al., 1998a). In agreement with this in KitL Δ9/Δ9 mice the numbers of mast cells in the skin and the peritoneum were reduced which is in accordance with the reduced plasma sKitL levels in these mice. "
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    ABSTRACT: Juxtamembrane signaling via the membrane growth factor KitL is critical for Kit mediated functions. KitL has a conserved cytoplasmic domain and has been shown to possess a monomeric leucine-dependent basolateral targeting signal. To investigate the consequences in vivo of impaired basolateral KitL targeting in polarized epithelial cells, we have mutated this critical leucine to alanine using a knock-in strategy. KitL(L263A/L263A) mutant mice are pigmented normally and steady-state hematopoiesis is unaffected although peritoneal and skin mast cell numbers are significantly increased. KitL localization is affected in the Sertoli cells of the KitL(L263A/L263A) testis and testis size is reduced in these mice due to aberrant spermatogonial proliferation. Furthermore, the effect of the KitL L263A mutation on the testicular phenotype is dosage dependent. The tubules of hemizygous KitL(L263A/Sl) mice completely lack germ cells in contrast to the weaker testicular phenotype of KitL(L263A/L263A) mice. The onset of the testis phenotype coincides with the formation of tight junctions between Sertoli cells during postnatal development. Thus, the altered sorting of KitL is dispensable for hematopoietic and melanogenic lineages, yet is crucial in the testicular environment, where the basal membranes of adjacent polarized Sertoli cells form a niche for the proliferating spermatogonia.
    Full-text · Article · Oct 2009 · Developmental Biology
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    • "Male, but not female mice carrying this mutation are infertile, though both sexes exhibit pigmentation deficiencies and anaemia. Defects in mice harbouring the Sl17H mutation have been shown to be the consequence of defective KL dimer formation, cellular processing and poor surface expression, suggesting that the cytoplasmic tail of KL itself does not have a direct role in signal transduction (Kapur et al., 1999; Tajima et al., 1998a). "
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    ABSTRACT: Paracrine signalling between the oocyte and its surrounding somatic cells is fundamental to the processes of oogenesis and folliculogenesis in mammals. The study of animal models has revealed that the interaction of granulosa cell-derived kit ligand (KL) with oocyte and theca cell-derived c-Kit is important for multiple aspects of oocyte and follicle development, including the establishment of primordial germ cells within the ovary, primordial follicle activation, oocyte survival and growth, granulosa cell proliferation, theca cell recruitment and the maintenance of meiotic arrest. Though little is known about the specific roles of KL and c-Kit during human oogenesis, the expression profiles for KL and c-Kit within the human ovary suggest that they are also functionally relevant to female fertility. This review details our current understanding of the roles of KL and c-Kit within the mammalian ovary, with a particular focus on the functional diversity of this receptor-ligand interaction at different stages of oocyte and follicle development.
    Full-text · Article · Mar 2006 · Molecular Human Reproduction
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    • "Furthermore, the finding that the temperature-sensitive kit allele fails to promote larval melanocyte regeneration at temperatures permissive for embryonic melanocyte development suggests that the kit j1e99 allele is partially compromised at 231C and 251C, and that the requirement for kit function is greater during larval melanocyte regeneration than that for other roles we have suggested, including embryonic melanocyte development and melanocyte regeneration in the regenerating fin (Rawls and Johnson, 2001). The different dose requirements of kit signaling between ontogenetic development and proliferation/regeneration have been reported in other systems, for instance, hematopoiesis in mice (Tajima et al, 1998). The kit j1e99 allele has a single nucleotide change resulting in a leucine-to-proline substitution in the 754 amino acid in the second tyrosine kinase domain of the kit receptor tyrosine kinase (Rawls and Johnson, 2003). "
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    ABSTRACT: A method to specifically ablate melanocytes in a genetically tractable organism would facilitate the analysis of melanocyte regeneration and regulation. We have demonstrated that a Q-switched neodymium:yttrium-aluminum-garnet dermatology laser kills larval melanocytes in zebrafish. Following melanocyte ablation, new melanocytes regenerate from unpigmented precursors. We show that melanocyte regeneration following laser ablation requires kit receptor tyrosine kinase.
    Full-text · Article · Dec 2004 · Journal of Investigative Dermatology
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