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Fil: Dalton, George. University of Texas Southwestern Medical Center. Department of Medicine; Estados Unidos Fil: An, Sung-Wan. University of Texas Southwestern Medical Center. Department of Medicine; Estados Unidos Fil: Al-Juboori, Saif I. University of Colorado Denver. Department of Electrical Engineering; Estados Unidos Fil: Nischan, Nicole. University of Texas Southwestern Medical Center. Department of Biochemistry; Estados Unidos Fil: Yoon, Joonho. University of Texas Southwestern Medical Center. Department of Medicine; Estados Unidos Fil: Dobrinskikh, Evgenia. University of Colorado Denver. Department of Medicine; Estados Unidos Fil: Hilgemann, Donald W. University of Texas Southwestern Medical Center. Department of Physiology; Estados Unidos Fil: Xie, Jian. University of Texas Southwestern Medical Center. Department of Medicine; Estados Unidos Fil: Luby-Phelps, Kate. University of Texas Southwestern Medical Center. Department of Cell Biology; Estados Unidos Fil: Luby-Phelps, Kate. University of Texas Southwestern Medical Center. Live Cell Imaging Core Facility; Estados Unidos Fil: Kohler, Jennifer J. University of Texas Southwestern Medical Center. Department of Biochemistry; Estados Unidos Fil: Birnbaumer, Lutz. Pontificia Universidad Católica Argentina. Facultad de Ciencias Médicas. Instituto de Investigaciones Biomédicas; Argentina Fil: Birnbaumer, Lutz. National Institute of Environmental Health Sciences. Neurobiology Laboratory; Estados Unidos Fil: Huang, Chou-Long. University of Texas Southwestern Medical Center. Department of Medicine; Estados Unidos Abstract: Soluble klotho, the shed ectodomain of the antiaging membrane protein α-klotho, is a pleiotropic endocrine/paracrine factor with no known receptors and poorly understood mechanism of action. Soluble klotho down-regulates growth factor-driven PI3K signaling, contributing to extension of lifespan, cardioprotection, and tumor inhibition. Here we show that soluble klotho binds membrane lipid rafts. Klotho binding to rafts alters lipid organization, decreases membrane's propensity to form large ordered domains for endocytosis, and down-regulates raft-dependent PI3K/Akt signaling. We identify α2-3-sialyllactose present in the glycan of monosialogangliosides as targets of soluble klotho. α2-3-Sialyllactose is a common motif of glycans. To explain why klotho preferentially targets lipid rafts we show that clustering of gangliosides in lipid rafts is important. In vivo, raft-dependent PI3K signaling is up-regulated in klotho-deficient mouse hearts vs. wild-type hearts. Our results identify ganglioside-enriched lipid rafts to be receptors that mediate soluble klotho regulation of PI3K signaling. Targeting sialic acids may be a general mechanism for pleiotropic actions of soluble klotho.

We report the development of an all-fiber-optic scanning endomicroscope capable of high-resolution second harmonic generation (SHG) imaging of biological tissues and demonstrate its utility for monitoring the remodeling of cervical collagen during gestation in mice. The endomicroscope has an overall 2.0 mm diameter and consists of a single customized double-clad fiber, a compact rapid two-dimensional beam scanner, and a miniature compound objective lens for excitation beam delivery, scanning, focusing, and efficient SHG signal collection. Endomicroscopic SHG images of murine cervical tissue sections at different stages of normal pregnancy reveal progressive, quantifiable changes in cervical collagen morphology with resolution similar to that of bench-top SHG microscopy. SHG endomicroscopic imaging of ex vivo murine and human cervical tissues through intact epithelium has also been performed. Our findings demonstrate the feasibility of SHG endomicroscopy technology for staging normal pregnancy, and suggest its potential application as a minimally invasive tool for clinical assessment of abnormal cervical remodeling associated with preterm birth.