L1 cell adhesion molecule (CD171)
Authors: Steve Silletti, Peter Altevogt, Anthony M P. Montgomery
Reviewer: Michael Hortsch
PROW 1:31-37(2000)

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OVERVIEW Summary Sentence

• CD171 (L1) is a multidomain cell adhesion molecule required for normal neurohistogenesis. Although designated a neural recognition molecule, CD171 is also expressed by certain epithelial cells and by some cells of lymphoid and myelomonocytic origin

Abstract

• CD171 is a transmembrane recognition molecule that belongs to the immunoglobulin supergene family. The CD171 ectodomain consists of six immunoglobulin-like domains followed by five fibronectin-like repeats (type III). The ectodomain is linked via a single transmembrane sequence to a conserved cytoplasmic domain of 110 or 114 amino acids {Moos_M/Schachner_M.1988.NATUR} . Mutations in the CD171 gene cause an X-linked neurological disorder in man termed CRASH (corpus callosum hypoplasia, retardation, aphasia, spastic paraplegia and hydrocephalus) {Brummendorf_T/Rathjen_FG.1998.CON} . Neuropathologies described in CD171 knockout mice resemble the CRASH phenotype and include dilated ventricles, abnormal dendritic architecture, and developmental defects in the hippocampus and corpus callosum {Cohen_NR/Furley_AJ.1998.CB} ; {Dahme_M/Mantei_N.1997.NG} ; {Haney_CA/Trapp_BD.1999.JCB} ; {Demyanenko_GP/Maness_PF.1999.JN} . Non-neuronal functions attributed to CD171 include branching morphogenesis in the kidney {Debiec_H/Ronco_PM.1998.JCB} , the maintenance of lymph node architecture during an immune response {Di_Sciullo_G/Bogen_SA.1998.JEM} and the co-stimulation of T-cell activation in vitro {Balaian_LB/Montgomery_AM.2000.EJI} . CD171 function in neurological processes has been attributed to homophilic L1-L1 ligation {Lemmon_V/Lagenaur_C.1989.NEURO} . However, CD171 has also been shown to support interactions with a variety of heterophilic ligands including proteoglycans, integrins, CD9 , CD24 , CD56 , TAG-1/Axonin-1, CD142 and CD166 {Hortsch_M.1996.NEURO} ; {Hortsch_M.2000.MCN}

Molecular Families

• Families in which CD171 is a member
  • CD171-->L1 adhesion molecules -->immunoglobulin supergene family

Names

• L1CAM [HUGO gene name]
• neural cell adhesion molecule L1 (N-CAM L1 )
• L1 cell adhesion molecule (L1 , L1CAM , CAML1 )
• NILE [rat]
• NgCAM [chick]
• E587 [goldfish]
• neuroglian [Drosophila]
• L1.1 [zebrafish]
• L1.2 [zebrafish]
• CD171

Major Links

• LocusLink: 3897
• Mendelian Inheritance in Man (OMIM): 308840
• SwissProt annotated protein record: P32004

Author's Additional Insights

• In vertebrate species several CD171-related genes are present, which include neurofascin, Nr-CAM and CH-L1**
• The contribution of homophilic L1-L1 interaction to neural developmental processes is now well established
• The functional significance of heterophilic CD171 interactions, and the role of nonneural CD171, is only now starting to be addressed

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SYSTEM VIEW Disease Relevance / Function in Vivo

• Mutations in the CD171 gene are responsible for an X-linked recessive neurological disorder in man (CRASH syndrome) associated with hydrocephalus due to stenosis of the aqueduct of Sylvius 1 (HSAS1, HSAS), mental retardation, aphasia, shuffling gait and adducted thumbs (MASA), spastic paraplegia type 1 (SPG1) and agenesis of the corpus callosum (ACC) {Brummendorf_T/Rathjen_FG.1998.CON}
• CD171-deficient mice have neuropathologies consistent with CRASH syndrome in man. Findings include:
  • dilated brain ventricles {Demyanenko_GP/Maness_PF.1999.JN}
  • a reduction in the size of the corticospinal tract with errors in corticospinal axon guidance {Cohen_NR/Furley_AJ.1998.CB}
  • abnormal morphogenesis of cortical dendrites and developmental defects in the hippocampus and corpus callosum {Dahme_M/Mantei_N.1997.NG}
  • a deficit in the association between axons and Schwann cells has been reported {Haney_CA/Trapp_BD.1999.JCB}
  • poor performance in spatial learning
• In Drosophila, mutations in the CD171-type gene neuroglian result in axonal pathfinding defects and embryonic lethality {Hall_SG/Bieber_AJ.1997.JN} **
• Fibroblasts genetically modified to express CD171 have been shown to promote nerve generation in rats {Kobayashi_S/Uyemura_K.1995.NL}
• Ethanol-mediated disruption of CD171-dependent processes has been suggested to be involved in the pathogenesis of alcohol-related neurodevelopmental disorders including fetal alcohol syndrome {Bearer_CF/Cheng_G.1999.JBC}
• Remodeling of lymph node reticular matrix during an immune response is blocked in mice by an anti-CD171 antibody {Di_Sciullo_G/Bogen_SA.1998.JEM}

Cellular Function

• Cell adhesion molecule that mediates homotypic and heterotypic cell-cell interaction
• Mediates dynamic neurological processes including neural cell migration, neurite extension, Schwann cell-axon interaction, synaptogenesis, myelination, neuronal cell survival, and the induction of long-term potentiation
• Supports the haptotatic migration and invasion of tumor cells
• Can function as a costimulatory molecule in T-cell activation in vitro {Balaian_LB/Montgomery_AM.2000.EJI}

Protein Location

• Transmembrane with recruitment to cell-cell interface
• Shed as large ectodomain fragments as a result of posttranslational cleavage
• Neuronal CD171 isoform is internalized via clathrin-coated vesicles

Cellular Expression

• Strong expression on human post-mitotic neurons of the CNS and PNS, on pre- or nonmyelinating Schwann cells of the PNS, and on glial cells
• Intermediate to low expression described on rodent epithelia associated with the kidney, skin, lung, small intestine, colon, urogenital tract, and tongue {Nolte_C/Schachner_M.1999.CTR}
• Intermediate to low expression is evident on human lymphoid and myelomonocytic cells including CD4+ T-cells, a subset of B-cells, monocytes, monocyte-derived dendritic cells (DC), and follicular DC in situ {Pancook_JD/Montgomery_AM.1997.JI}
• Intermediate expression on murine lymph node reticular fibroblasts {Di_Sciullo_G/Bogen_SA.1998.JEM}
• Strong to intermediate expression described on human tumor cells including neuroectodermal tumor cell lines (melanoma and neuroblastoma), carcinomas (lung, renal, and skin) and monocytic leukemias

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GENE Gene Sequence Links

• No information

Chromosomal Location

• Xq28 [human]

Gene Polymorphism

• No information

Transcription Regulating Molecules

Transcription_Factor	Comment
Pax-6	Pax-6 binds to the CD171 promoter
HoxA-1	HoxA-1 binds to the CD171 promoter
neural restrictive silencer element (NRSE)	NRSE can act as both a repressor and enhancer of CD171 gene expression

Gene Annotation

• No information

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TRANSCRIPT Transcript Sequence Links

• GenBank Accession Code: M77640 , NM_000425 [Reference sequence derived from M77640.1]

Post-transcriptional Modification

• The CD171 gene comprises 29 exons of which 28 are coding exons
• Exons 2 and 27 are neural-specific

Transcript Annotation

• CD171 expression is induced by the bone morphogenic proteins BMP-2 and BMP-4, as well as NGF

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PROTEIN Biochemical Activity

• Signaling mediated by CD171 binding can occur through cis interactions with other molecules or through CD171 itself
• CD171 signaling involves phosphorylation as described (see section: Enzymes for which this is a Substrate ) as well as recruitment of the cytoskeletal element ankyrin{Crossin_KL/Krushel_LA.2000.DD} [review]; {Davis_JQ/Bennett_V.1993.JCB} ; {Dubreuil_RR/Hortsch_M.1996.JCB} *
• Interaction with the membrane skeleton is regulated by CD171 adhesive activity**
• Internalization of CD171 promotes activation of members of the MAP kinase cascade in a src-dependent manner. This pathway involves phosphotidylinositol-3-kinase and Rac-1 {Schmid_RS/Maness_PF.2000.JN} ; {Schaefer_AW/Lemmon_V.1999.JBC}
• CD171 signaling has also been shown to involve pertussis toxin-sensitive g-proteins, protein kinase C, the release of arachidonic acid and influx of intracellular calcium through L- and N-type channels {Williams_EJ/Doherty_P.1994.JN}

Protein Sequence Links

• SwissProt annotated protein record: P32004

Protein Sequence Annotation

• Six immunoglobulin domains amino terminal to five fibronectin type III repeats on the extracellular face, followed by a single pass transmembrane domain and an 114 or 110 amino acid cytoplasmic domain {Moos_M/Schachner_M.1988.NATUR}
• An attractive model for the overall structure of CD171 is based on the crystal structure of a related molecule called axonin-1/TAG-1;according to this model the first four immunoglobulin domains of CD171 family members bind to one another in an antiparallel alignment {Freigang_J/Welte_W.2000.CELL} *

Protein Polymorphism

• No information

Protein Physical Properties

Cell_Type	MW_unreduced	MW_reduced	Comment
Neurons	200 and 180-190 kDa		Smaller MW band is faint
Neurons	140, 80 and 40 kDa		Cell-associated degradation products
Neuroblastoma	200-215 kDa		Single band reported
Melanoma	215-220 and 190-200 kDa		Smaller MW band is faint
Monocytes	210-220 kDa		Single band reported
T-cells	200-220 kDa		Size of band varies with T-cell activation
Epithelial cells	220-230 and 190-210 kDa		Two separate bands reported

Post-translational Modification

• CD171 is glycosylated, containing 21 potential N-Linked glycosylation sites within its ectodomain*
• Six potential phosphorylation sites are present in the CD171-cytoplasmic domain
• Conserved dibasic sequences in the third fibronectin-like domain of CD171 are susceptible to serine protease cleavage
• Plasmin cleaves within the sequence RK¯HSK¯RH⁸⁴⁶{Nayeem_N/Montgomery_AM.1999.JCS}
• Membrane proximal cleavage by a disintegrin metalloproteinase (ADAM) has been shown to result in the release of the CD171 ectodomain {Beer_S/Altevogt_P.1999.JCS}

Protein Structure Links

• CD171: PDB Structure Identifier: 1CFB [Crystal structure or neuroglian in Drosophila Melanogaster], 1CS6 [Potentially relevant crystal structure of Axonin-1/Tag-1 in Gallus Gallus], 1BIH [Crystal structure of hemolin in Hyalophora Cecropia]

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MOLECULAR INTERACTIONS Molecular Pathways

• (see section: Enzymes for which this is a Substrate )

Enzymes for which this is a Substrate

Enzyme	Comment
p90rsk	Phosphorylates serine 1152 of the CD171 cytoplasmic domain
Casein kinase II	Phosphorylates serine 1181 of the CD171 cytoplasmic domain
ERK-2	Phosphorylates serine 1204 and serine 1248 of the CD171 cytoplasmic domain
CEK5	Tyrosine phosphorylation of CD171 by the Eph kinase CEK5 has been demonstrated

Substrates

• No intrinsic catalytic domains are present in CD171

Other Ligands and Associated Molecules

Molecule	Comment
CD171	See NOTE1
Neurocan	See NOTE1
Phosphocan	See NOTE1
Laminin	See NOTE1
CD9	See NOTE2
CD24 (heat stable antigen)	See NOTE2
CD56 (NCAM)	See NOTE2
Axonin-1/TAG-1	See NOTE2
CD51/CD61 (alpha-v beta-3)	See NOTE3
CD41/CD61 (alpha-IIb beta-3)	See NOTE3
CD49e/CD29 (VLA-5 or alpha-5 beta-1)	See NOTE3
alpha-9 /CD29 (beta-1)	See NOTE3
ankyrins	See NOTE4
kinases	See NOTE4

• NOTE1: trans (molecules on the apposing cell) interacting elements include CD171 (homophilic), neurocan, phosphocan, and laminin
• NOTE2: cis (molecules on the same cell) interacting elements described include CD9 , CD24 (heat stable antigen), CD56 (NCAM), Axonin-1/TAG-1
• NOTE3: integrins reported to recognize CD171 include CD51/CD61 (alpha-v beta-3), CD41/CD61(alpha-IIb beta-3), CD49e/CD29 (VLA-5 or alpha-5 beta-1), and alpha-9 beta-1 {Silletti_S/Montgomery_AM.2000.JCB}
• NOTE4: CD171 cytoplasmic domain interacts with ankyrin and kinases (see section: Enzymes for which this is a Substrate ) and (see section: Enzymes for which this is a Substrate )

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REAGENTS Model Animal Strains

Species_or_Strain	Supplier	Comment
Heterozygous CD171 (±) female mice	Dr Philippe Soriano (Fred Hutchinson Cancer Research Center)	Heterozygous CD171 (±) female mice on a 129/SvJae congenic background {Bearer_CF/Cheng_G.1999.JBC}
nrg1	Dr. Michael Hortsch (University of Michigan)	Protein null mutation See NOTE**
nrg2	Dr. Michael Hortsch (University of Michigan)	Protein hypomorph mutations See NOTE**
nrg3	Dr. Michael Hortsch (University of Michigan)	Temperature sensitive mutation See NOTE**

• NOTE: Three balanced Drosophila stocks exist with neuroglian mutations {Hall_SG/Bieber_AJ.1997.JN} **

Monoclonal Antibodies

mAb	Supplier	Comment
5G3	BD Pharmingen ( 15551A )	Epitope is in amino-terminal Ig-like domain. Does not recognize CD171 expressed by CD4+ T-cells
L1 mAb	BD Transduction Lab (L30220)	mouse mAb for Western blot**
L1 Ab-1	Lab Vision - NeoMarkers (MS-770-P1)	mAb for Western, IP**

Polyclonal Antibodies

Antibody	Supplier	Comment
NCAM-L1 (C-20)	Santa Cruz ( sc-1508 )	Western blots, reacts with human and rodent, goat polyclonal IgG**

Drugs and Small Molecules

• Not commercially available

Genetic Constructs

• Not commercially available

Purified Protein

• Not commercially available

Reagents Misc.

• Not commercially available

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REFERENCES References

REVIEWS
1. {Crossin_KL/Krushel_LA.2000.DD}
Crossin KL, Krushel LA. 2000. Cellular signaling by neural cell adhesion molecules of the immunoglobulin superfamily. Dev Dyn 218:260-279
2. {Hortsch_M.1996.NEURO}
Hortsch M. 1996. The L1 family of neural cell adhesion molecules: old proteins performing new tricks. Neuron 17:587-593
3. {Hortsch_M.2000.MCN}
Hortsch M. 2000. Structural and functional evolution of the L1 family: are four adhesion molecules better than one?. Mol Cell Neurosci 15:1-10

PRIMARY CITATIONS
4. {Balaian_LB/Montgomery_AM.2000.EJI}
Balaian LB, Moehler T, Montgomery AM. 2000. The human neural cell adhesion molecule L1 functions as a costimulatory molecule in T cell activation. Eur J Immunol 30:938-943
5. {Bearer_CF/Cheng_G.1999.JBC}
Bearer CF, Swick AR, O'Riordan MA, Cheng G. 1999. Ethanol inhibits L1-mediated neurite outgrowth in postnatal rat cerebellar granule cells. J Biol Chem 274:13264-13270
6. {Beer_S/Altevogt_P.1999.JCS}
Beer S, Oleszewski M, Gutwein P, Geiger C, Altevogt P. 1999. Metalloproteinase-mediated release of the ectodomain of L1 adhesion molecule. J Cell Sci 112:2667-2675
7. {Brummendorf_T/Rathjen_FG.1998.CON}
Brummendorf T, Kenwrick S, Rathjen FG. 1998. Neural cell recognition molecule L1: from cell biology to human hereditary brain malformations. Curr Opin Neurobiol 8:87-97
8. {Cohen_NR/Furley_AJ.1998.CB}
Cohen NR, Taylor JS, Scott LB, Guillery RW, Soriano P, Furley AJ. 1998. Errors in corticospinal axon guidance in mice lacking the neural cell adhesion molecule L1. Curr Biol 8:26-33
9. {Dahme_M/Mantei_N.1997.NG}
Dahme M, Bartsch U, Martini R, Anliker B, Schachner M, Mantei N. 1997. Disruption of the mouse L1 gene leads to malformations of the nervous system. Nat Genet 17:346-349
10. {Davis_JQ/Bennett_V.1993.JCB}
Davis JQ, McLaughlin T, Bennett V. 1993. Ankyrin-binding proteins related to nervous system cell adhesion molecules: candidates to provide transmembrane and intercellular connections in adult brain. J Cell Biol 121:121-133 **
11. {Debiec_H/Ronco_PM.1998.JCB}
Debiec H, Christensen EI, Ronco PM. 1998. The cell adhesion molecule L1 is developmentally regulated in the renal epithelium and is involved in kidney branching morphogenesis. J Cell Biol 143:2067-2079
12. {Demyanenko_GP/Maness_PF.1999.JN}
Demyanenko GP, Tsai AY, Maness PF. 1999. Abnormalities in neuronal process extension, hippocampal development, and the ventricular system of L1 knockout mice. J Neurosci 19:4907-4920
13. {Di_Sciullo_G/Bogen_SA.1998.JEM}
Di Sciullo G, Donahue T, Schachner M, Bogen SA. 1998. L1 antibodies block lymph node fibroblastic reticular matrix remodeling in vivo. J Exp Med 187:1953-1963
14. {Dubreuil_RR/Hortsch_M.1996.JCB}
Dubreuil RR, MacVicar G, Dissanayake S, Liu C, Homer D, Hortsch M. 1996. Neuroglian-mediated cell adhesion induces assembly of the membrane skeleton at cell contact sites. J Cell Biol 133:647-655 **
15. {Freigang_J/Welte_W.2000.CELL}
Freigang J, Proba K, Leder L, Diederichs K, Sonderegger P, Welte W. 2000. The crystal structure of the ligand binding module of axonin-1/TAG-1 suggests a zipper mechanism for neural cell adhesion. Cell 101:425-433
16. {Hall_SG/Bieber_AJ.1997.JN}
Hall SG, Bieber AJ. 1997. Mutations in the Drosophila neuroglian cell adhesion molecule affect motor neuron pathfinding and peripheral nervous system patterning. J Neurobiol 32:325-340
17. {Haney_CA/Trapp_BD.1999.JCB}
Haney CA, Sahenk Z, Li C, Lemmon VP, Roder J, Trapp BD. 1999. Heterophilic binding of L1 on unmyelinated sensory axons mediates Schwann cell adhesion and is required for axonal survival. J Cell Biol 146:1173-1184
18. {Kobayashi_S/Uyemura_K.1995.NL}
Kobayashi S, Miura M, Asou H, Inoue HK, Ohye C, Uyemura K. 1995. Grafts of genetically modified fibroblasts expressing neural cell adhesion molecule L1 into transected spinal cord of adult rats. Neurosci Lett 188:191-194
19. {Lemmon_V/Lagenaur_C.1989.NEURO}
Lemmon V, Farr KL, Lagenaur C. 1989. L1-mediated axon outgrowth occurs via a homophilic binding mechanism. Neuron 2:1597-1603
20. {Moos_M/Schachner_M.1988.NATUR}
Moos M, Tacke R, Scherer H, Teplow D, Fruh K, Schachner M. 1988. Neural adhesion molecule L1 as a member of the immunoglobulin superfamily with binding domains similar to fibronectin. Nature 334:701-703
21. {Nayeem_N/Montgomery_AM.1999.JCS}
Nayeem N, Silletti S, Yang X, Lemmon VP, Reisfeld RA, Stallcup WB, Montgomery AM. 1999. A potential role for the plasmin(ogen) system in the posttranslational cleavage of the neural cell adhesion molecule L1. J Cell Sci 112:4739-4749
22. {Nolte_C/Schachner_M.1999.CTR}
Nolte C, Moos M, Schachner M. 1999. Immunolocalization of the neural cell adhesion molecule L1 in epithelia of rodents. Cell Tissue Res 298:261-273
23. {Pancook_JD/Montgomery_AM.1997.JI}
Pancook JD, Reisfeld RA, Varki N, Vitiello A, Fox RI, Montgomery AM. 1997. Expression and regulation of the neural cell adhesion molecule L1 on human cells of myelomonocytic and lymphoid origin. J Immunol 158:4413-4421
24. {Schaefer_AW/Lemmon_V.1999.JBC}
Schaefer AW, Kamiguchi H, Wong EV, Beach CM, Landreth G, Lemmon V. 1999. Activation of the MAPK signal cascade by the neural cell adhesion molecule L1 requires L1 internalization. J Biol Chem 274:37965-37973
25. {Schmid_RS/Maness_PF.2000.JN}
Schmid RS, Pruitt WM, Maness PF. 2000. A MAP kinase-signaling pathway mediates neurite outgrowth on L1 and requires Src-dependent endocytosis. J Neurosci 20:4177-4188
26. {Silletti_S/Montgomery_AM.2000.JCB}
Silletti S, Mei F, Sheppard D, Montgomery AM. 2000. Plasmin-sensitive dibasic sequences in the third fibronectin-like domain of L1-cell adhesion molecule (CAM) facilitate homomultimerization and concomitant integrin recruitment. J Cell Biol 149:1485-1502
27. {Williams_EJ/Doherty_P.1994.JN}
Williams EJ, Walsh FS, Doherty P. 1994. The production of arachidonic acid can account for calcium channel activation in the second messenger pathway underlying neurite outgrowth stimulated by NCAM, N-cadherin, and L1. J Neurochem 62:1231-1234

WWW Resources
28. L1CAM Mutation Web Page

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* indicates amended by reviewer, ** indicates added by reviewer
Modified 09/10/01 mpr@mail.nih.gov