RESUMO
BACKGROUND: Transmembrane and immunoglobulin domain-containing protein 1 (TMIGD1) is a recently identified cell adhesion molecule which is predominantly expressed by epithelial cells of the intestine and the kidney. Its expression is downregulated in both colon and renal cancer suggesting a tumor suppressive activity. The function of TMIGD1 at the cellular level is largely unclear. Published work suggests a protective role of TMIGD1 during oxidative stress in kidney epithelial cells, but the underlying molecular mechanisms are unknown. RESULTS: In this study, we address the subcellular localization of TMIGD1 in renal epithelial cells and identify a cytoplasmic scaffold protein as interaction partner of TMIGD1. We find that TMIGD1 localizes to different compartments in renal epithelial cells and that this localization is regulated by cell confluency. Whereas it localizes to mitochondria in subconfluent cells it is localized at cell-cell contacts in confluent cells. We find that cell-cell contact localization is regulated by N-glycosylation and that both the extracellular and the cytoplasmic domain contribute to this localization. We identify Synaptojanin 2-binding protein (SYNJ2BP), a PDZ domain-containing cytoplasmic protein, which localizes to both mitochondria and the plasma membrane, as interaction partner of TMIGD1. The interaction of TMIGD1 and SYNJ2BP is mediated by the PDZ domain of SYNJ2BP and the C-terminal PDZ domain-binding motif of TMIGD1. We also find that SYNJ2BP can actively recruit TMIGD1 to mitochondria providing a potential mechanism for the localization of TMIGD1 at mitochondria. CONCLUSIONS: This study describes TMIGD1 as an adhesion receptor that can localize to both mitochondria and cell-cell junctions in renal epithelial cells. It identifies SYNJ2BP as an interaction partner of TMIGD1 providing a potential mechanism underlying the localization of TMIGD1 at mitochondria. The study thus lays the basis for a better understanding of the molecular function of TMIGD1 during oxidative stress regulation.
Assuntos
Células Epiteliais/metabolismo , Glicoproteínas de Membrana/metabolismo , Proteínas de Membrana/metabolismo , Mitocôndrias/metabolismo , Membranas Mitocondriais/metabolismo , Adesão Celular/genética , Linhagem Celular Tumoral , Membrana Celular/metabolismo , Citoplasma/metabolismo , Glicosilação , Humanos , Moléculas de Adesão Juncional/genética , Moléculas de Adesão Juncional/metabolismo , Glicoproteínas de Membrana/genética , Proteínas de Membrana/genética , Mitocôndrias/genética , Domínios PDZ/genética , Ligação ProteicaRESUMO
The behavior of a cell depends on how its adhesion molecules interact with the cellular microenvironment. Hemidesmosomal collagen XVII essentially contributes to cell adhesion and modulates keratinocyte directionality and proliferation during skin regeneration, however only little is known about the involved interactions. Here, we used keratinocytes from patients with junctional epidermolysis bullosa with late onset, which exclusively produce a collagen XVII mutant with the p.R1303Q mutation within its extracellular C-terminus. Although this mutant was normally expressed and targeted to the membrane and the expression of integrins α3ß1, α6ß4 and of laminin-332 was unchanged, the keratinocytes were less adhesive, showed migratory defects and decreased clonogenic growth. Since the p.R1303Q substitution is located within the predicted laminin-332 binding site of collagen XVII, we anticipated an altered collagen XVII-laminin-332 interaction. Indeed, the pR1303Q collagen XVII ectodomain showed decreased binding capability to laminin-332 and was less co-localized with pericellular laminin-332 molecules in cell culture. Thus, aberrant collagen XVII-laminin-332 interaction results in reduced cell adhesion, destabilized cell motility and decreased clonogenicity, which in turn lead to blister formation, delayed wound healing and skin atrophy.
Assuntos
Substituição de Aminoácidos , Autoantígenos/química , Autoantígenos/metabolismo , Moléculas de Adesão Celular/metabolismo , Epidermólise Bolhosa Juncional/metabolismo , Colágenos não Fibrilares/química , Colágenos não Fibrilares/metabolismo , Idade de Início , Autoantígenos/genética , Sítios de Ligação , Adesão Celular , Movimento Celular , Proliferação de Células , Células Cultivadas , Epidermólise Bolhosa Juncional/genética , Humanos , Queratinócitos/citologia , Queratinócitos/metabolismo , Colágenos não Fibrilares/genética , Ligação Proteica , Domínios Proteicos , Calinina , Colágeno Tipo XVIIRESUMO
Endothelial cells line blood and lymphatic vessels and form intercellular junctions, which preserve vessel structure and integrity. The vascular endothelial cadherin, VE-cadherin, mediates endothelial adhesion and is indispensible for blood vessel development and permeability regulation. However, its requirement for lymphatic vessels has not been addressed. During development, VE-cadherin deletion in lymphatic endothelial cells resulted in abortive lymphangiogenesis, edema, and prenatal death. Unexpectedly, inducible postnatal or adult deletion elicited vessel bed-specific responses. Mature dermal lymph vessels resisted VE-cadherin loss and maintained button junctions, which was associated with an upregulation of junctional molecules. Very different, mesenteric lymphatic collectors deteriorated and formed a strongly hyperplastic layer of lymphatic endothelial cells on the mesothelium. This massive hyperproliferation may have been favored by high mesenteric VEGF-C expression and was associated with VEGFR-3 phosphorylation and upregulation of the transcriptional activator TAZ Finally, intestinal lacteals fragmented into cysts or became highly distended possibly as a consequence of the mesenteric defects. Taken together, we demonstrate here the importance of VE-cadherin for lymphatic vessel development and maintenance, which is however remarkably vessel bed-specific.