Bidirectional Transport by Distinct Populations of COPI-Coated Vesicles

Boukhelifa

Tribble

et al. 2008

MBoC

131

Phosphoinositides (PIPs) are ubiquitous regulators of signal transduction events in eukaryotic cells. PIPs are degraded by various enzymes, including PIP phosphatases. The integral membrane Sac1 phosphatases represent a major class of such enzymes. The central role of lipid phosphatases in regulating PIP homeostasis notwithstanding, the biological functions of Sac1-phosphatases remain poorly characterized. Herein, we demonstrate that functional ablation of the single murine Sac1 results in preimplantation lethality in the mouse and that Sac1 insufficiencies result in disorganization of mammalian Golgi membranes and mitotic defects characterized by multiple mechanically active spindles. Complementation experiments demonstrate mutant mammalian Sac1 proteins individually defective in either phosphoinositide phosphatase activity, or in recycling of the enzyme from the Golgi system back to the endoplasmic reticulum, are nonfunctional proteins in vivo. The data indicate Sac1 executes an essential household function in mammals that involves organization of both Golgi membranes and mitotic spindles and that both enzymatic activity and endoplasmic reticulum localization are important Sac1 functional properties. INTRODUCTIONSpatial and temporal regulation of intracellular signaling in eukaryotic cells involves the compartmentalization of membrane surfaces into discrete, albeit often transient, functional units. There are several biochemical strategies by which cells generate such units or domains. One well-established strategy uses the chemical diversity offered by phosphoinositides (PIPs), i.e., phosphorylated forms of phosphatidylinositol (PtdIns) (Majerus, 1997;Fruman et al., 1998;Strahl and Thorner, 2007). The chemical heterogeneity of individual PIP species permits the construction of chemically unique platforms on membrane surfaces that, in turn, recruit unique cohorts of proteins that drive specific biological reactions. Spatial and temporal control of such reactions requires a finely coordinated balance between the activities of the lipid kinases that produce PIPs and the activities of enzymes that degrade them. PIP turnover is catalyzed by two general classes of enzymes: phospholipases and PIP phosphatases.Although experimental scrutiny of the phospholipases has historically been more intense, recent demonstrations of the significant biological functions played by PTEN, the myotubularins, and synaptojanins highlight the general importance of PIP phosphatases (Wishart et al., 2001;Wishart and Dixon, 2002;Wenk and De Camilli, 2004).The SAC domain derives from the yeast Sac1 protein (ySac1; Cleves et al., 1989), and it represents a signature for PIP phosphatase catalytic activity . PIP phosphatases such as phosphatase and tensin homolog (mutated in multiple advanced cancers 1) (PTEN) (Maehama et al., 2001), synaptojanins (Cremona et al., 1999), and synaptojanin-like proteins (Srinivasan et al., 1997;Stolz et al., 1998) all harbor SAC domains. The prototypical member of this family, ySac1, catalyzes the dephosphoryla...

Section: Functional Distinction Between Mammalian Sac1 and Arf Depletionmentioning

confidence: 99%

The Sac1 Phosphoinositide Phosphatase Regulates Golgi Membrane Morphology and Mitotic Spindle Organization in Mammals

Boukhelifa

Tribble

et al. 2008

MBoC

131

“…Additionally, the COP I coat functions in retrograde transport and perhaps also in anterograde transport, within the Golgi complex (Orci et al, 1997;Pelham and Rothman, 2000). The minimal machinery for the budding of COP I-coated vesicles consists of coatomer, a stable cytosolic complex comprising seven equimolar subunits, ␣-, ␤-, ␤Ј-, ␥-, ␦-, ⑀-, and -COP, and the small GTPase ARF in its GTP-bound form (Rothman and Wieland, 1996;Spang et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

The α- and β′-COP WD40 Domains Mediate Cargo-selective Interactions with Distinct Di-lysine Motifs

Eugster

Frigerio

Dale

et al. 2004

MBoC

102

107

Coatomer is required for the retrieval of proteins from an early Golgi compartment back to the endoplasmic reticulum. The WD40 domain of ␣-COP is required for the recruitment of KKTN-tagged proteins into coatomer-coated vesicles. However, lack of the domain has only minor effects on growth in yeast. Here, we show that the WD40 domain of ␤ -COP is required for the recycling of the KTKLL-tagged Golgi protein Emp47p. The protein is degraded more rapidly in cells with a point mutation in the WD40 domain of ␤ -COP (sec27-95) or in cells lacking the domain altogether, whereas a point mutation in the Clathrin Heavy Chain Repeat (sec27-1) does not affect the turnover of Emp47p. Lack of the WD40 domain of ␤ -COP has only minor effects on growth of yeast cells; however, absence of both WD40 domains of ␣-and ␤ -COP is lethal. Two hybrid studies together with our analysis of the maturation of KKTN-tagged invertase and the turnover of Emp47p in ␣-and ␤ -COP mutants suggest that the two WD40 domains of ␣-and ␤ -COP bind distinct but overlapping sets of di-lysine signals and hence both contribute to recycling of proteins with di-lysine signals.

“…1989; Orci et al. 1997). Genome‐wide association studies revealed that one mutation in Golgb1 Y1212C (rs3732410) appeared to have a dominant effect: the overall significance of this variant with a reduced risk of ischemic stroke in all sickle cell anemia (SCA) patients with stroke against control SCA patients (OR = 0.27; 95% CI = 0.14–0.52) (Katayama et al.…”

Section: Discussionmentioning

confidence: 99%

Polymorphisms in three genes are associated with hemorrhagic stroke

Ge²,

et al. 2015

Brain and Behavior

BackgroundMultiligand receptor for advanced glycation end products (RAGE), osteoprotegerin, and Golgb1 genes may be implicated in atherosclerosis and vascular diseases. Single nucleotide polymorphisms (SNPs) rs1035798 in RAGE gene, rs2073617 and rs2073618 in TNFRSF11B, and rs3732410 in Golgb1 will be investigated on whether there is an association with hemorrhagic stroke (HS) in Chinese population.MethodsA total of 600 subjects including 199 HS patients and 401 controls were assayed. These samples were divided into two groups: the ≤50 year and >50 year groups. Genotyping of SNPs was determined using the SEQUENOM MassARRAY matrix‐assisted laser desorption ionization–time‐of‐flight–mass spectrometry. The association between genotype and HS risk was evaluated by computing the odds ratio (OR) and 95% confidence interval (CI) with multivariate unconditional logistic regression analyses.ResultsOur data showed that in the ≤50 year group, the rs1035798 major allele homozygote C/C in RAGE gene was associated with an increased risk of HS, while Golgb1 rs3732410 minor allele homozygote G/G was associated with a decreased risk of HS. In the >50 year group, the major allele homozygote G/G of rs2073618 was found to be associated with an increased risk of HS.ConclusionsThe polymorphisms rs1035798 of RAGE gene, rs2073618 of TNFRSF11B, and rs3732410 of Golgb1 might be involved in the risk of HS at different stage of ages.