RACK1, a New ADAM12 Interacting Protein

Abstract

ADAM12 belongs to a disintegrin-like and metalloproteinase-containing protein family that possesses multidomain structures composed of a pro-domain, a metalloprotease, disintegrin-like, cysteine-rich, epidermal growth factor-like, and transmembrane domains, and a cytoplasmic tail. Overexpression of several ADAMs has been reported in human cancer, and we recently described the involvement of ADAM12 in liver injury (Le Pabic, H., Bonnier, D., Wewer, U. M., Coutand, A., Musso, O., Baffet, G., Clement, B., and Theret, N. (2003 ADAMs 2 (a disintegrin and metalloproteinase domain) are a family of cell surface multidomain proteins involved in ectodomain shedding, cell adhesion, and cell signaling (2-5). Common domains to ADAM proteins include propeptide, metalloprotease, disintegrin, cysteine-rich, EGF-like, transmembrane and cytoplasmic domains. More than 30 members have been identified in the ADAM family with broad tissue distribution and have been implicated in highly diverse biological processes, including spermatogenesis/fertilization, neurogenesis, and inflammatory response. In recent years, increased expression of several ADAMs has been reported in human cancers (6 -11) and biological properties of ADAMs suggest an important role in cancer processes including cell adhesion, migration, survival, and proliferation (12, 13). Thus, we have recently described the up-regulation of ADAM12 mRNA levels in patients with hepatocellular carcinoma and the association of ADAM12 expression with liver tumor aggressiveness (1).ADAM12 is expressed as two spliced forms, the secreted form (ADAM12S) has been described as an active metalloprotease that cleaves IGFBP-3 and -5 (14 -16). In addition, by shedding the membrane-bound HB-EGF, ADAM12 was shown to promote cardiac hypertrophy (17) and by cleaving gelatin, fibronectin, and gelatinase IV, ADAM12 was suggested to facilitate tumor invasion in breast cancer (8). The role of ADAM12 in cell-cell and cell-matrix interactions has been supported by the interaction with ␤1-integrin (18, 19) and syndecans (20). The membrane-anchored long form of ADAM12 has a cytoplasmic tail that interacts with several SH3 domain containing proteins including the Src-kinase SRC and YES1 (21), the adapter proteins Grb2 (21) and Fish (22), the regulatory subunit of phosphatidylinositol 3-kinase, p85␣ (17), and PACSIN3, a cytoplasmic phosphoprotein that plays a role in vesicle trafficking (23). In addition, the ADAM12 tail interacts with eve-1, a EEN binding protein that acts as an adaptor module to inhibit the Ras stimulating activity of Sos2 (24) and ␣-actinin-2, an actin cross-linking protein highly expressed in skeletal and cardiac muscle (25). More recently, the role of ADAM12 in modulating the transforming growth factor-␤ signaling pathway has been suggested by the interaction of ADAM12 with both FLRG (follistatin-related gene), binding proteins to transforming growth factor-␤ superfamily members (26), and the transforming growth factor type II receptor (T␤RII) leading to an increase in transforming gr...

Leucine-Rich Repeat Kinase 2 Binds to Neuronal Vesicles through Protein Interactions Mediated by Its C-Terminal WD40 Domain

“…Accordingly, we observed a severe reduction in the transport of synaptotagmin-labeled (cycling) SV to distal parts of neuronal processes upon overexpression of LRRK2 WD40 domain constructs; such output might be read as a dominant negative effect of ectopic LRRK2 WD40 executed on endogenous LRRK2 function. RACK1 is a seven-bladed WD40 propeller protein (19,40), reported to bind and anchor recycling endosomal vesicles to centrosomes (57). Accordingly, we reported that RACK1 significantly reduces SV recycling (but not spatial segregation) once it is overexpressed in neurons and that it cosediments with pure SV.…”

“…The LRRK2 WD40 G2385R variant as well as FLAG-and RFP-tagged LRRK2 consisting of residues 1 to 2141 (hereinafter termed LRRK2 1-2141) were generated by site-directed mutagenesis using a QuikChange mutagenesis kit (Stratagene). Cloning of pGEX-RACK1 and full-length FLAG-LRRK2 was described previously (18)(19)(20). LRRK2 WD40 consisting of aa 2148 to 2527 with six copies of a His tag (6ϫHis) was cloned into pETM11.…”

A disintegrin and metalloproteinase-12 (ADAM12): Function, roles in disease progression, and clinical implications

“…These include various cancers [27,51,52,53,54,55,56,57,58,59], liver fibrogenesis [60], cardiac hypertrophy [61], and asthma [62]. There is also evidence to suggest that increases in ADAM12 are associated with adverse outcomes in pregnancy [63,64,65], and that it may also be used as a first [66] or second [67,68] trimester screen for Down syndrome, although these data are considerably more debated.…”

“…Bourd-Boittin et al ., have demonstrated that ADAM12 is a binding partner for the receptor for activated protein kinase C (RACK1), a homolog of the β-subunit of heterotrimeric G proteins [60]. Both RACK1 and ADAM12 are overexpressed in patients with hepatic carcinomas.…”

“…By treating human hepatic stellate cells from partial hepatectomy patients with PMA (phorbol 12-myristate 13-acetate, used as an activator of PKC [72]), they demonstrate that translocation of ADAM12 to the cell surface is modulated by PKC activity. They further suggest that upstream from this phenomenon, type I collagen (a hallmark of the injured liver [73]) interacts with β-integrin, activating PKC, and allowing the translocation of ADAM12 to the cell surface via a RACK1-dependent pathway 9 [60]. Once at the cell surface, ADAM12 may contribute to cell spreading and cancer progression.…”