The molecular understanding of autophagy has originated almost exclusively from yeast genetic studies. Little is known about essential autophagy components specific to higher eukaryotes. Here we perform genetic screens in C. elegans and identify four metazoan-specific autophagy genes, named epg-2, -3, -4, and -5. Genetic analysis reveals that epg-2, -3, -4, and -5 define discrete genetic steps of the autophagy pathway. epg-2 encodes a coiled-coil protein that functions in specific autophagic cargo recognition. Mammalian homologs of EPG-3/VMP1, EPG-4/EI24, and EPG-5/mEPG5 are essential for starvation-induced autophagy. VMP1 regulates autophagosome formation by controlling the duration of omegasomes. EI24 and mEPG5 are required for formation of degradative autolysosomes. This study establishes C. elegans as a multicellular genetic model to delineate the autophagy pathway and provides mechanistic insights into the metazoan-specific autophagic process.

Summary The prostate epithelial lineage hierarchy and the cellular origin for prostate cancer remain inadequately defined. Using a lineage tracing approach, we show that adult rodent prostate basal and luminal cells are independently self-sustained in vivo. Disrupting the tumor suppressor Pten in either lineage led to prostate cancer initiation. However, the cellular composition and onset dynamics of the resulting tumors are distinctive. Prostate luminal cells are more responsive to Pten null-induced mitogenic signaling. In contrast, basal cells are resistant to direct transformation. Instead, loss of Pten activity induces the capability of basal cells to differentiate into transformation-competent luminal cells. Our study suggests that deregulation of epithelial differentiation is a critical step for the initiation of prostate cancers of basal cell origin.

The ability to isolate prostate stem cells is essential to explore their role in prostate development and disease. In vitro prostate colonyand sphere-forming assays were used to quantitatively measure murine prostate stem/progenitor cell enrichment and self-renewal. Cell surface markers were screened for their ability to positively or negatively enrich for cells with enhanced growth potential in these assays. Immunohistochemical and FACS analyses demonstrate that specific cell surface markers can be used to discriminate prostate stromal (CD34 ؉ ), luminal epithelial (CD24 ؉ CD49f ؊ ), basal epithelial (CD24 ؉ CD49f ؉ ), hematopoietic (CD45 ؉ , Ter119 ؉ ), and endothelial (CD31 ؉ ) lineages. Sorting for cells with a CD45 ؊ CD31 ؊ Ter119 ؊ Sca-1 ؉ CD49f ؉ antigenic profile results in a 60-fold enrichment for colony-and sphere-forming cells. These cells can self-renew and expand to form spheres for many generations and can differentiate to produce prostatic tubule structures containing both basal and luminal cells in vivo. These cells also localize to the basal cell layer within the region of the gland that is proximal to the urethra, which has been identified as the prostate stem cell niche. Prostate stem cells can be isolated to a purity of up to 1 in 35 by using this antigenic profile. The remarkable similarity in cell surface profile between prostate and mammary gland stem cells suggests these markers may be conserved among epithelial stem cell populations.CD49f ͉ integrin ␣6 ͉ Sca-1 ͉ CD24 heat-stable antigen ͉ stem cell niche S tem cells are of interest clinically because of their potential to repair damaged tissues, treat degenerative diseases, and because of their purported role in tumor initiation. The ability to identify and isolate stem cells is necessary to study their specialized biology. Enrichment for many types of tissue stem cells has been achieved by using cell surface markers. Murine hematopoietic stem cells can be enriched by sorting Lin Ϫ Thy-1 lo Sca-1 ϩ ckit ϩ cells from the bone marrow (1). Recent studies suggest that even better purity can be achieved by further sorting based on expression of the SLAM family receptors CD150 and CD48 (2). Bronchioavelolar stem cells can be isolated from their niche at the bronchioalveolar duct junction (BADJ) by sorting cells with a CD45 Ϫ CD31 Ϫ Sca-1 ϩ CD34 ϩ profile (3). Data from two recent reports show that mouse mammary stem cells possess a Lin Ϫ Sca-1 ϩ CD140a Ϫ CD24 ϩ CD49f ϩ CD29 ϩ cell surface profile and can be isolated to a purity of up to 1 in 20 by using subsets of these markers (4, 5).The presence of stem cells in the prostate first was proposed to explain the seemingly inexhaustible capacity of the organ to regenerate during androgen cycling experiments (6). The identification of side-population cells and replication quiescent BrdU label-retaining cells further suggests that stem cells exist in the gland (7,8). Several studies have enriched for primitive prostate cells by using cell surface markers. Richardson et al. (9) demonstrated that th...

Prostate cancer is the most commonly diagnosed malignancy among men in industrialized countries, accounting for the second leading cause of cancer-related deaths. While we now know that the androgen receptor (AR) is important for progression to the deadly advanced stages of the disease, it is poorly understood what AR-regulated processes drive this pathology. Here, we demonstrate that AR regulates prostate cancer cell growth via the metabolic sensor 5′-AMP-activated protein kinase (AMPK), a kinase that classically regulates cellular energy homeostasis. In patients, activation of AMPK correlated with prostate cancer progression. Using a combination of radiolabeled assays and emerging metabolomic approaches, we also show that prostate cancer cells respond to androgen treatment by increasing not only rates of glycolysis, as is commonly seen in many cancers, but also glucose and fatty acid oxidation. Importantly, this effect was dependent on androgen-mediated AMPK activity. Our results further indicate that the AMPK-mediated metabolic changes increased intracellular ATP levels and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α)-mediated mitochondrial biogenesis, affording distinct growth advantages to the prostate cancer cells. Correspondingly, we used outlier analysis to determine that PGC-1α is overexpressed in a subpopulation of clinical cancer samples. This was in contrast to what was observed in immortalized benign human prostate cells and a testosterone-induced rat model of benign prostatic hyperplasia. Taken together, our findings converge to demonstrate that androgens can co-opt the AMPK-PGC-1α signaling cascade, a known homeostatic mechanism, to increase prostate cancer cell growth. The current study points to the potential utility of developing metabolic-targeted therapies directed towards the AMPK-PGC-1α signaling axis for the treatment of prostate cancer.

MicroRNAs (miRNAs) and small interfering RNAs (siRNAs) are two types of noncoding RNAs involved in developmental regulation, genome maintenance, and defense in eukaryotes. The activity of Dicer or Dicer-like (DCL) proteins is required for the maturation of miRNAs and siRNAs. In this study, we cloned and sequenced 66 candidate rice (Oryza sativa) miRNAs out of 1,650 small RNA sequences (19 to approximately 25 nt), and they could be further grouped into 21 families, 12 of which are newly identified and three of which, OsmiR528, OsmiR529, and OsmiR530, have been confirmed by northern blot. To study the function of rice DCL proteins (OsDCLs) in the biogenesis of miRNAs and siRNAs, we searched genome databases and identified four OsDCLs. An RNA interference approach was applied to knock down two OsDCLs, OsDCL1 and OsDCL4, respectively. Strong loss of function of OsDCL1IR transformants that expressed inverted repeats of OsDCL1 resulted in developmental arrest at the seedling stage, and weak loss of function of OsDCL1IR transformants caused pleiotropic developmental defects. Moreover, all miRNAs tested were greatly reduced in OsDCL1IR but not OsDCL4IR transformants, indicating that OsDCL1 plays a critical role in miRNA processing in rice. In contrast, the production of siRNA from transgenic inverted repeats and endogenous CentO regions were not affected in either OsDCL1IR or OsDCL4IR transformants, suggesting that the production of miRNAs and siRNAs is via distinct OsDCLs.